(FORTUNE Magazine) – Until now, cars with pricetags over $100,000 have had the aura of collector's items. Superluxury automakers -- Rolls-Royce, Ferrari, Lamborghini, and their ilk -- count annual production in the hundreds, not thousands. But Mercedes- Benz and Porsche are racing to introduce ultrapowerful high-tech cars aimed at combining such prices with mass-market appeal. Mercedes-Benz is updating its popular S class of luxury sedans next year. The sticker price of the top-of-the-line model, the 600 SEL, is expected to top $100,000, up at least 35% from the 1990 model. Due in the U.S. in 1992, the 600 SEL will have a 400-horsepower, 12-cylinder engine, photochromatic glass -- the tint changes with lighting conditions -- and state-of-the-art electronics. Says John Wolkonowicz, an auto consultant at Arthur D. Little: ''It will be the finest auto in the world.'' Porsche has announced that its 1991 911 Turbo will list at $95,000, a 34% jump over the price of last year's model. With a 315-hp engine, the car will also be a lot more powerful -- it'll hit 60 mph in less than five seconds. But will thousands of paying customers shell out this kind of money for production-line cars? Auto analysts seem to think so. Says George Peterson of AutoPacific Group in Santa Ana, California: ''A $100,000 pricetag is not a barrier anymore. Some people may see it as a plus.'' - M.A.