SAN FRANCISCO -- SanDisk ( SNDK) posted a greater-than-expected loss in the third quarter, as prices for its flash memory chips plunged 30% quarter over quarter. The Milpitas, Calif., chipmaker managed to outpace Wall Street's lackluster sales expectations, delivering $821 million in revenue, vs. the $778 million expected by Wall Street analysts. At this time last year, SanDisk had sales of $1.04 billion. With the market for NAND flash memory chips awash in oversupply, and prices for the chips under severe pressure, SanDisk was forced to sell its chips markedly below its own production costs. The company said its product gross margin in the third quarter was negative 20%, compared to 3.3% in the second quarter, and 24.3% at this time last year. SanDisk reported a net loss of $155.2 million, or 69 cents a share, vs. net income of 84.6 million, or 36 cents a share in the year-ago period. Excluding stock compensation expenses and other charges, SanDisk said it lost 59 cents a share. The average analyst expectation called for SanDisk to lose 27 cents a share, according to Thomson Reuters. The company's results included $109 million in inventory-related charges. Shares of SanDisk were down 36 cents, or 2.5%, to $14.06 in after-hours trading on Monday. SanDisk's financial report follows a separate announcement by the company earlier Monday in which it said that Toshiba was buying 30% of its manufacturing capacity at a pair of chip factories that the two firms jointly own.