Record profits grow out of record prices, and whether the market maintains any momentum may have less to do with interest rates than window stickers. "Prices are rising faster than incomes, and that's not good," says General Motors Corp. President John F. Smith Jr. in a speech to dealers at the National Automobile Dealers Assn. in Dallas. "It's a warning flag out there." Average sticker prices at the $20,000 mark concern more than Mr. Smith. A recent study of car buyers by the Dohring Co. notes that 62.1% of buyers polled say the high price of new vehicles is forcing them to consider buying used vehicles instead.