TOKYO, DEC. 1 (SATURDAY) -- The long wait is over. After years of gee-whiz talk, magazine cover stories and trade-show demonstrations, the product widely touted as a technological wave of the future -- high-definition television -- is finally on the market.

Today, three big Japanese electronics companies begin offering HDTV sets for sale. With prices of early models ranging upwards of $30,000, the sets are aimed, for now at least, at video professionals rather than ordinary consumers.

But industry officials expect a few hundred to be sold for home use even before the price starts coming down. "If a rich consumer can afford it, he can buy," said a spokesman for Matsushita Electric Industrial Co.

The commercial advent of HDTV -- a television system that provides pictures in much more vivid and crisp detail than conventional TV -- has been argued by many experts as being as significant for the TV industry as was the replacement of black and white with color.

But whether the development has any importance beyond the TV industry is a matter of hot dispute. To hear some tell it, today marks a historic milestone, one that could become a significant point in America's economic decline.

The HDTVs that go on sale today "will be the first in a market predicted to range from $8 billion to $80 billion worldwide by the year 2000, and the United States may not be a major player if Washington's current policies are not radically changed," said John Stern, Tokyo representative of the American Electronics Association.

By failing to support the development of a U.S. HDTV industry, the government "has sold America's birthright for a Walkman," Stern charged.

Nonsense, say others. Today's development "provides food for thought, but not cause for hand wringing," said Kenneth Flamm, a senior fellow at the Brookings Institution, who contends that HDTV is not nearly as crucial a technological advance as it has been cracked up to be.

Everyone agrees on this much: Japanese companies are far ahead in the HDTV race, with the Europeans a distant second and American companies, so far, a poor third.

Not only have Japanese firms poured vast sums into developing the technology, but the state-owned NHK network already provides one hour a day of "Hi-Vision" broadcasts and plans to increase that to eight hours next summer.

U.S. companies, meanwhile, are a long way from producing HDTV equipment that can compete, and the first high-definition broadcasts in the United States are not expected until the mid-1990s, well after the resolution of a complicated debate over technical standards.

U.S. experts who tend toward the alarmist view contend that Japanese dominance in HDTV will lead to similar results in other key industries.

HDTV sets, they note, are loaded with large amounts of computer chips, so HDTV could become the driving force behind chip development over the next couple of decades.

Moreover, efforts to design extraordinarily compact HDTV "displays" -- TV monitors as flat as a picture that could be hung on a living room wall -- could lead to all sorts of spinoffs in businesses as diverse as home entertainment and radar.

Skeptics question this logic. They argue that the more important market is computers, where the United States still has a strong lead.

American firms, said Brookings's Flamm, "don't have to reenter consumer electronics" to develop technologies such as advanced TV monitors, because the U.S. computer industry already is making major strides in that direction.

Japan's HDTV system, some American analysts say, is based on outmoded technology and does not improve over today's TV by very much.

These analysts say the United States would do better to leap-frog it and build sets based on the "digital" language of computers. They would be used to channel into American homes not just football and sitcoms but computer services and video conferencing as well. Several U.S. companies are working on this technology.

Whichever system is adopted, many analysts believe much of the production would be based in the United States.

Some critics even question whether HDTV is likely to catch on with consumers. The sets are expensive -- they are likely to cost at least $3,000 apiece, even after a mass market is established -- and the best conventional TVs already offer excellent picture quality.

At an HDTV display on the ground floor of a Sony Corp. office building in Tokyo's Ginza district, opinion among consumers was mixed.

"The size is rather big for a Japanese home," said Keijiro Suzuki, a 39-year-old advertising agency official, referring to the 36-inch-wide screen, adding that he would rather spend the money on a new car.

But most passersby seemed dazzled by the images on the screen, and some said they would pay as much as $7,500 for a system like Sony's.

Japanese consumers won't be able to simply walk into an electronics shop and buy an HDTV; for the time being, at least, they will have to order them from Sony, Matsushita (maker of the Panasonic brand) and NEC Corp.

The companies haven't made a push to attract consumers, because of the limited amount of "Hi-Vision" programming available.

Still, the fact that it is Japanese consumers, and not Americans, who are getting first crack at the product underscores what has happened to the U.S. electronics industry over the past two decades, said Roger Mathus, director of the Semiconductor Industry Association's Tokyo office.

Mathus recalled the era in the 1960s when the then-flourishing U.S. television industry began marketing color sets.

"Color TV was launched in the U.S., because that's where the industry was centered," he said.