Zillow, the real estate website known for estimating house values, said on Tuesday that it would stop flipping houses and planned to lay off about a quarter of its employees amid heavy losses while disclosing expected losses of more than $550 million on homes purchased in the second half of this year for which the company admits it paid too much.

208 homes that Zillow owns in Phoenix, for instance, 93% were listed for less than what it paid. In Dallas, where Zillow owns 168 homes, about 81% of its properties were listed for less than what the company bought them for.

One Atlanta property that Zillow purchased in June at $501,200 is now listed for $459,900 after it was listed at $551,900 — an almost $100,000 drop in expected yield.

The real-estate giant on Tuesday blamed a faulty algorithmic model for ditching its iBuying business of buying and selling homes quickly, and said it will lay off about a quarter of its staff. The surprising exit, announced with pedestrian quarterly profits, thrashed shares in another rough trading session Tuesday, a day after an analyst said two-thirds of the homes it bought are underwater.