In addition to giant tubs of mayonnaise and mega-packs of toilet paper, thousands of Costco shoppers are finding room in their carts for a more high-end product: plasma TV sets.

Sharp price cuts have brought plasma sets and other thin, flat televisions out of high-end electronics boutiques and into thousands of mass-market outlets such as Costco, a wholesale buying club.

The least expensive plasma sets still cost a hefty $3,000 or more, yet sales are growing so rapidly that many manufacturers are racing to boost production.

“Everyone has been surprised by the quantities that have moved,” said Tim Farmer, a vice president at Issaquah, Wash.-based Costco Wholesale Corp.

The burgeoning popularity of thin-screen televisions has prompted ever more manufacturers to jump into the fray. In all, more than two dozen companies now market some version of the product.

That increase, combined with expanding production capacity and improved technology, could push the price of plasma sets down by one-third next year, according to analyst Richard Doherty of Envisioneering Group, a technology research firm.

“There is strong consumer demand, but not enough to stop the free fall,” Doherty said.

Manufacturers already are selling the core component of a plasma set — the glass panel — at or near a loss in their hunger for a share of the growing market, some industry analysts say.

The demand for thin screens is fueled in part by the advent of DVDs and digital TV broadcasts, which offer more detailed pictures and more lifelike colors than conventional analog TV signals. To see the difference, consumers need a set that can pack more information onto the screen than their current televisions can.

This sharpness is most vivid on screens that are 40 inches diagonal or larger. At that size, however, traditional direct-view and projection televisions are so bulky that many consumers have trouble finding a place for them at home. Hence the interest in thin screens — models svelte and light enough to hang on a wall.

The glass panels at the heart of plasma and LCD sets come mainly from about a dozen companies with factories in Japan, Korea and, increasingly, China. About 800,000 plasma panels will be shipped this year around the world, said Mark McConnaughey, senior vice president of the advanced technology group of Viewsonic Corp. of Walnut, Calif.

Ed Hawkins, manager at Kief's Audio-Video, shows off a plasma television available for sale at the store, 24th and Iowa streets. Hawkins said the flat-screen sets were available in sizes up to 61 inches.

That is minuscule compared with the overall market for televisions, which is about 140 million sets this year. Still, McConnaughey said 2003 would be a “breakout year” for plasma because shipments should double.

Helping drive the growth are new or expanded manufacturing facilities. For example, Japanese electronics giant NEC Corp. doubled the capacity of its factory in Japan this year, reaching 300,000 to 400,000 plasma panels. And it plans to double it again in 2003, officials said.

Meanwhile, plants are becoming far more efficient, slashing the cost per unit. The average factory had to scrap or rework 85 percent of the panels produced three years ago, but now rejects only 10 percent, said Tom Edwards, senior analyst at NPD Techworld, a research firm.

As competition has heated up during the past four years, prices have fallen more than 50 percent. According to NPD Techworld, the average price of a plasma display sold in the United States dropped from $12,700 in January 1999 to $6,100 in October 2002.

Prices will have to drop significantly more, however, to attract masses of buyers, said Tamaryn Pratt, an analyst at Quixel Research in New York. A Quixel survey found that more than 70 percent of consumers interviewed want screens larger than 40 inches but they quickly lose interest in sets that cost more than $2,000.

Like plasma sets, LCD televisions carry a premium price — they can be 10 times as expensive as a comparable tube-driven television — that knocks them out of most buyers’ budgets.

By Pratt’s estimates, 250,000 to 300,000 will be sold in the United States this year. The challenge for LCD television makers is to build screens larger than 20 inches that aren’t prohibitively expensive.

Sharp Electronics Corp., for one, is betting heavily on LCDs, a gamble that it expects will pay off first in Japan. Its chairman, Toshiaki Urushisako, has predicted that Sharp will switch completely from conventional tube sets to LCD televisions in Japan by 2005.

Bob Scaglione, a marketing vice president at Sharp, said he expected prices to drop 15 percent to 20 percent annually on LCD televisions.

Prices have dropped even more dramatically on sets using Texas Instruments Inc.’s digital light processing technology, a slim approach to projection televisions that nonetheless can’t be mounted on the wall.

The least expensive set is a 43-inch model due soon from Samsung that will sell for about $3,700 — not cheap, but far below the $12,000 to $15,000 price tags on earlier generations, said John Reder, a manager at Texas Instrument.

Two years from now, he added, the company’s goal is to make digital-light-processing sets as inexpensive to produce as conventional projection sets.