(FORTUNE Magazine) – Who doesn't fantasize about island living? Pristine beaches, perfect sunsets...oh, and hordes of summer renters, celebrity-wranglers, million-dollar inland lots, and other perks of living in a "discovered" paradise. Below are three hot spots priced for the old bull market and three affordable oases that should surge in value in time for the next one. --Melanie Shanley

If You Can't Drop a Million or More...

FISHER ISLAND, FLA. Average home price $2.5 million Average building lot price N.A. Construction costs N.A. Developer Dan McLean has bought most of the 216-acre island and plans to continue building and selling homes in the $2.5 million price range.

NANTUCKET, MASS. Average home price $1 million Average building lot price $467,000 Construction costs $400-$500/sq. ft. Think prices are outrageous? They've slid nearly 50% from last year as many New Yorkers choose for getaways closer to home (and that don't require a flight).

BLOCK ISLAND, R.I. Average home price $1.3 million Average building lot price $500,000 Construction costs $350-$450/sq. ft. When lots hit the market in this preppy haven, they're usually snatched up by the well-funded land preservation trust, forcing out other bidders.

Opt for a Bargain Instead

AMELIA ISLAND, FLA. Average home price $224,300 Average building lot price $165,800 Construction costs $125-$400/sq. ft. Amelia Island Plantation, a planned community, is the poshest spot; untouched beaches are still available to those looking to build for less.

PLUM ISLAND, MASS. Average home price $288,500 Average building lot price $350,000-$400,000 Construction costs $125-$200/sq. ft. Not to be confused with its New York counterpart, Plum is on the verge of becoming a luxury locale. A modern sewage system is now being installed.

SAN JUAN ISLANDS, WASH. Average home price $277,000 Average building lot price $200,000 Construction costs $150-$400/sq. ft. Mansions like Paul Allen's sit alongside hippie huts in this chain of 172 islands. Inland lots are still cheap, and oceanfront spots abundant.