HAVANA, Cuba—Listed at $1.2 million, the penthouse has broad terraces, marble floors and stunning waterfront views stretching from the Darth Vader-style Russian Embassy to Meyer Lansky’s old Riviera hotel. That might seem pricey for a Communist country whose average worker earns around $20 a month. But owner John Jefferis, a 57-year-old hotelier from Bermuda, says his target buyer belongs to a different demographic altogether. “There are very few apartments that can be legally purchased by foreigners, and when there’s a limited supply of something, usually there’s a premium for the price,” says Mr. Jefferis, who adds that jet-setters like his expat neighbors here can probably afford to splurge. “It’s not their first or second or third home, put it like that.” It is all part of a real-estate revolution sweeping Cuba.