The Owner's Course · Module 4
Valuation and Comparables
There is no Zestimate for an island. Prices are set in a thin, opaque market where two similar-looking properties can trade five-fold apart — and both trades can be rational. This module is about building your own defensible number, so that when you negotiate, you are standing on evidence rather than on the seller's brochure.
Begin with a truth that surprises most first-time buyers: the majority of private islands that come to market never sell at their original asking price, and a substantial share never sell at all. Marketing periods of two to five years are unremarkable. This is not because the market is broken; it is because sellers anchor to sentiment and buyers anchor to nothing. The buyer who arrives with a reasoned valuation is often the only person in the transaction holding one.
The trouble with the per-acre number
Per-acre pricing is the first figure every listing offers and the least useful one. On the mainland, an acre is roughly fungible: it sits in a grid of comparable acres, served by the same roads and utilities. An island acre is not fungible even with the acre beside it. A ten-acre island with two acres of elevated, buildable ground and a protected deep-water approach is worth more — often several times more — than a forty-acre island that is mostly mangrove, floods at spring tide, and can only be reached by shallow-draft boat at half-tide or better.
Illustrative spreads make the point. Undeveloped islands off Nova Scotia or in Scandinavian archipelagos have typically traded anywhere from the tens of thousands to a few hundred thousand pounds in total, working out to figures as low as £5,000–£30,000 per acre. Freehold cays in the Bahamas or Exumas commonly ask £150,000–£800,000 per acre, and small developed islands near Nassau or in the British Virgin Islands can imply well over £1 million per acre. The land is not fifty times better; the climate, tenure, access and buyer pool are different markets entirely. Dividing price by acreage collapses all of that into one meaningless quotient.
An island is not priced by the acre. It is priced by the usable acre, the reachable acre, and the acre you are legally permitted to build on — and those are usually a small fraction of the total.
Assembling a comparable set
Because islands trade rarely, you cannot restrict your comparables to "islands like this one that sold nearby last year". There may be none. The working method is to cast a wide net and then adjust, rather than to find perfect matches.
Cast across regions and years
Gather ten to twenty data points: closed sales where possible, plus asking prices with time-on-market as a weak signal. Go back five to ten years and correct roughly for time — island values in most regions have moved broadly with prime coastal property, though with fatter tails in both directions. A sale from 2018 is still informative if you adjust it; an asking price from last month may be pure hope. Public registries in Canada, the United States, Scandinavia and the UK often disclose closed prices; in much of the Caribbean and Central America you will rely on brokers' knowledge, and the honest ones will tell you the difference between what was asked and what was paid. Our notes on the quiet market explain why a meaningful share of island transactions never appear on a portal at all, and how to get sight of them anyway.
Normalise before you compare
For each comparable, record the same dozen facts: total and buildable acreage, tenure, distance and travel time from the nearest airport with scheduled service, deep-water access, existing structures and their condition, utilities in place, permits or zoning attached, and the year and currency of the transaction. A one-page grid of this kind — the same discipline we apply in an Island Dossier — turns anecdotes into a dataset, however small.
The four adjustments that matter
With the raw set in hand, you adjust each comparable towards the subject island. Four variables carry most of the weight. The percentages below are illustrative of the ranges we typically observe, not a formula.
| Variable | What moves value | Typical swing |
|---|---|---|
| Access | Under 30 minutes from an international airport versus a multi-leg journey; all-tide dock versus beach landing; helipad or airstrip potential | ±30–50% |
| Tenure | Clean freehold versus long leasehold, Crown lease, or structures required for foreign ownership | Leasehold often 20–50% below freehold equivalent |
| Infrastructure | Working dock, power, water and habitable buildings versus raw land — credit at depreciated value, not cost | Often only 30–60% of original build cost |
| Buildability | Elevation, setback lines, environmental designations, an existing permit or master plan | A consented plan can add 10–25%; a protected designation can remove most development value |
Two cautions. First, existing improvements are routinely overvalued by sellers, who remember what they spent. A dock built fifteen years ago in a hurricane belt may be a liability, not an asset; salt-air attrition means island structures depreciate faster than their mainland cousins. Second, access adjustments compound with everything else, because access governs construction cost, staffing, insurance and your own willingness to visit — the theme of our guide to island access and transport. An island you reach in forty minutes gets used forty weekends a year; one that takes a day gets used four times, and resale buyers price that in.
Replacement cost: the sobering anchor
For a developed island, the most clarifying exercise is to price the alternative: buy the best comparable raw island, then build the same estate today. Offshore construction typically runs 1.5 to 3 times mainland cost once barging, labour housing and logistics are counted — Module 5 and our guide to building on a private island treat this in detail. If a turnkey island asks £12 million and your replacement maths says raw land at £3 million plus £6 million of construction and three years of your life, the ask is defensible. If replacement comes to £5 million, the £7 million balance is a premium for time and provenance, and you should decide consciously whether you are willing to pay it. Sellers of well-built islands often recover only 50–70 pence per pound of development spend; that arithmetic is your quiet advantage as a buyer and your caution as a future owner.
Income capitalisation for working islands
Where an island trades as a business — a boutique resort, an established rental villa — a third lens applies. Take sustainable net operating income after realistic management, staffing, maintenance and reserve costs (island reserves should be generous; see what a private island really costs), and capitalise it. Remote hospitality assets typically command capitalisation rates of roughly 8–12%, meaningfully higher than mainland hotels, reflecting weather risk, keyman dependence and thin resale markets. A working island producing £400,000 of durable net income supports perhaps £3.5–5 million on income grounds. If the ask is £9 million, the seller is pricing a trophy, not a business — which is legitimate, but you should not pay a trophy price and underwrite it with a business case.
Scarcity, trophies, and where the premium evaporates
Genuine scarcity value exists. Freehold islands within thirty minutes of a major airport, in politically stable jurisdictions, with elevation, water and all-weather access, are counted in the dozens worldwide, and they command premiums that survive downturns. The premium evaporates one tier down: islands that are merely remote, merely pretty, or compromised on tenure or access behave like illiquid land, not like trophies. In soft markets the top tier reprices by 10–15% while the middle simply stops trading. If you are paying a scarcity premium, satisfy yourself that the scarcity is real — that the attribute commanding the premium (the airstrip, the anchorage, the freehold) cannot be replicated by the next listing.
Reading the ask-vs-appraisal gap
Asking prices for islands routinely sit 20–40% above any defensible appraisal, and time-on-market is the tell. An island freshly listed at a full price is a seller testing the water. The same island three years and two price cuts later is a seller being educated by the market — and your comparable set should record that education. Ask the broker directly for price history and previous under-offers; the answers, and the hesitations, are data. Discounts from original ask of 20–35% on eventual island sales are common enough that opening 25–30% below a stale ask, with your reasoning attached, is not aggressive — it is orthodox.
Negotiating from a defensible number
The point of all this work is not precision — no island valuation is precise — but posture. Arrive with a one-page memo: comparable grid, the four adjustments, replacement cost, income value if relevant, and a concluded range. Offer within it and share the logic. Sellers who have waited years for a buyer rarely walk away from a reasoned number; they walk away from numbers that feel arbitrary. Condition the price on what your diligence has not yet confirmed — tenure, permits, the survey — using the sequence set out in how to buy a private island, and let our ownership calculator keep the running costs honest inside your total commitment. None of this is a formal valuation, and where lenders or estates are involved you will want a credentialed appraiser in the relevant jurisdiction; if you would like help framing the brief, write to us through the enquiry form.
- I have gathered at least ten comparable data points, including closed sales, across regions and years — not just current listings.
- I know the buildable acreage of the subject island, not merely the total acreage.
- I have adjusted comparables for access, tenure, infrastructure and buildability, and written the adjustments down.
- I have credited existing structures at depreciated value, informed by survey, not at the seller's recollected cost.
- I have run replacement cost: best raw comparable plus today's offshore build cost at 1.5–3× mainland rates.
- For any income story, I have capitalised realistic net income at 8–12% and compared it with the ask.
- I can name the specific scarce attribute any premium is attached to, and I believe it cannot be replicated.
- I know this listing's full price history, time on market, and any prior failed offers.
- My concluded range is written in a memo I would be comfortable showing the seller's side.
- My offer strategy conditions price on unresolved diligence rather than assuming the brochure is true.