One by one, tycoons who built their wealth on China’s economic rise have been giving up their trophy homes in Hong Kong.

Two apartments in a Frank Gehry glass-and-steel tower that twists out of the mountainside. Three European-style mansions with turrets and swimming pools. Four white villas sitting in a row.

All but two of the properties have already sold for tens of millions of dollars each. And while it might be hard to believe, each one was a steal — snatched up for discounts of one-third to more than half of the previous values.

Hong Kong’s housing market has long had an are-you-kidding-me feel to it. For nearly 20 years, property prices have climbed higher and higher, turning it into one of the most unaffordable cities in the world, where the poor rented subdivided apartments so small they were colloquially known as “coffin homes.”

Now, many of the same people who contributed to the housing market’s inequities, from the builders to the wealthy speculators, have found themselves being forced to sell their prized homes fast. Their riches had swelled with an unfathomable rise in China’s real estate market, and its collapse and aftermath have left many short on cash.

Most notable among them is Hui Ka Yan of the onetime property giant China Evergrande. Creditors seized his European-style homes, which were collectively worth more than $190 million, after the company collapsed. One of them sold this year for $58 million, less than half of the $130 million that a company tied to Evergrande and Mr. Hui had paid for it in 2009, according to the global real estate firm Knight Frank.