Uber and other ride-hail apps have upended all that.

Just as homeowners faced ruin when housing markets sank, struggling cab owners in Chicago, Boston, San Francisco and other cities are now facing foreclosure and bankruptcy. Many took out loans to pay for taxi medallions, counting on business that has instead nose-dived amid fierce competition. They are falling behind on loan payments, being turned away by lenders and stand to lose not only the medallions that are their livelihoods but also their homes and savings.

Nowhere is the crisis more dire than in New York, which has the largest taxi fleet in the country. Medallions now sell for a fraction of the record $1.3 million price in 2014, and in many cases, are worth far less than what their owners borrowed to buy them. Even if these owners sell their medallions, they still owe hundreds of thousands of dollars — far more than in many other cities where medallion prices were lower to begin with.

In an unprecedented fire sale of medallions, up to 46 of them are expected to go on the auction block later this month as part of bankruptcy proceedings against taxi companies affiliated with an embattled taxi mogul. While the city has previously held auctions to sell a limited number of new medallions — about 1,800 since 1996 — this is believed to be the first auction to dispose of foreclosed medallions, according to city officials.

While the auction has drawn attention to the precipitous fall of the once-mighty taxi industry, it does not reflect the hardship — and heartbreak — of individual owners like Mr. Isac. It is their stories that often get lost in the larger debate over new technology and commutes, and tell of the human cost of the city’s rapidly evolving transportation landscape.

Since 2015, a total of 85 medallions have been sold as part of foreclosure proceedings, according to city records. In August alone, 12 of the 21 medallion sales were part of foreclosures; the prices of all the sales ranged from $150,000 to $450,000 per medallion.