By this time next month, when the hectic, last-minute productin crises are over and "Star Trek -- The Motion Picture" is playing nationwide to audiences swept by a multimedia promotional campaign, executives at Paramount Pictures will have on their hands what probably will be the most expensive film ever produced.

Seventeen months in the making with a price tag reliably estimated att $43.5 million, the science fiction extravaganza will have cost nearly three times as much as the total spent on the 79 episodes of the original television series of the late 1960s.

But although the lavish sums spent on "Star Trek" prompt consternation among Hollywood's more conservation fiscal sentinels, what is most remarkable is that the space epic is only one of a growing group of motion pictures whose costs have skyrocketed.

The average amount major studios spend producing a silm has risen gradually over the decades, but the figure has almost doubled from $4 million in 1976 to $7.5 million this year, according to the Motion Picture Associatin of America. The averages have been boosted by the increase in the number of particularly-high-cost motion pictures that are being turned out.

With the continuing setting of records for box office grosses, there are "some producers (who) are trying to hit a home run every time they step up to bat," noted Peter. Geiger, vice president in the entertainment division of Bank of America, explaining the increasing rate at which high-budget motion pictures are being made.

"Everybody in the business is trying to put out another "Star Wars" or "Jaws" agreed Max Youngstein, one of the founders of United Artists, now a consultant to independent movie producers. "They're looking for the kill," he said.

For George Lucas, "Star Wars," which he directed, meant virtual financial independence as a film maker. Twentieth Century Fox financed the $7 million release and split the merchandising evenly with Lucas. In addition, Fox received a 60 percent distribution fee, while thee remainder went to Lucas.

In contrast, Lucasfilm Ltd. is financing the $20 million-plus sequel to "Star Wars," "The Empire Strikes Back." Lucas also reportedly will receive the entire distribution fee.

Other films costing megabucks that either are in production or have been released recently include the following:

Thirty million dollars or more -- "Flash Gordon" (Dino De Laurentiis Productions/Universal Pictures), "Apocalypse Now" (Francis Ford Coppola/UA), "Moonraker" (UA), "Heaven's Gate" (UA), "Star Trek" (Paramount).

Twenty million dollars or more "King Kong" (De Laurentiis/Paramount), "A bridge Too Far" (Joseph E. Levine/UA), "The Sorcerer" (Universal/Paramount), "The Wiz" (Paramount), "Hurricane" (De Laurentiis), "1941" (universal/Columbia Pictures Industries Inc.), "Blues Brothers" (Fox) and "The Day the World Ended" (Warner Brothers).

Fifteen million dollars or more -- "The Black Hole" (Walt Disney Productions), "Caligula" (penthouse Folms), "The Brinks Job" (De Laurentiis/Universal), "Towering Inferno" (Fox/Warner), "Meteor" (American International Pictures/Warner), and "All That Jazz" (Columbia /Fox).

In addition to the rising costs attributable to inflation, other reasons for the increase in production costs are the sumptuous salaries which bigname stars command, and higher earnings negotiated by the powerful motion picture craft unions.

The money spent on promoting motion pictures has risen concomitantly, due mainly to the increased use of television advertisements. In 1973 the motion picture industry spent $273.1 million advertising in the media. The 1979 projection for media expenditures runs to $652 million.

Six years ago, an average major film's ad campaign was between $1 million and $2 million. Today the average spent on promotion is about $4 million -- more for especially expensive films. Paramount is expected to spend more than $8 million to market "Star Trek," for instance.

Forming the backdrop for this upsurge in the economics of the film business is the fact that the industry is experiencing what veteren observer Art Murphy described as "a long-term upward cycle."

The fair-weather era in the motion picture business has made the major studios more amenable to catering to the wishes of their creative talents. If a star is in demand, he or she knows that should one studio not meet his or her wishes, the next one will, explained a studio vice president.

Superstars such as Steve McQueen or Robert Redford can command$3 million a film. For less important actors such as Ryan O'Neal or Nick Nolte, " $1 million seems to be the going rate," said a knowledgeable studio executive. Well-known writers and directors start at half a million dollars a picture, he said.

Directors are being given more latitude in financial affairs despite their lack of management expertise, said Murphy, who currently directs a graduate program in studio management at the University of Southern California.

More money also is being spent on special effects. New techniques in producing opticals have spawned a highly competitive industry.Despite the recent surge in effects films, the technology is at a relatively early stage of development. Movies which employ lavish special effects rely on custom designing and construction of computers, cameras and other equipment. One reliable source predicted that $26 million eventually will be spent on "Star Trek's" special effects alone. Time-consuming problems with the special effects, including a change in contractors, even will delay the first screening for the press by one day.

With the advent of television, the years 1946 through 1971 constituted a quarter-century-long decline in the theatrical film business, said Murphy.

By 1962 domestic box-office grosses had fallen to nearly half the $1.69 billion posted in 1946. Subsequently the industry experienced a gradual rise in cinema attendance, but it was not until 1974 that the 1946 mark was surpassed.

The late '60s and early '70s were austere years for the movie business. Betwen 1968 and 1971, the industry recorded losses of about $525 million. Major studio production was down, and unemployment was up. Twentieth Century Fox alone lost $116.6 million between 1969 and 1971, and the studio paid no dividends from 1970 to 1972.

The breakdown of censorship, the emergence of major independent producers, together with the availability of tax-shelter financing, helped revitalize the sagging industry in the early part of the decade. Blockbusters such as Fox's "The French Connection" and Paramounts's "Love Story" provided an extra shot in the arm and brought audiences back to the theaters.

By the early 1970s, box-office smashes were upon us -- starting with Paramount's "The Godfather" in 1972 and Universal's "Jaws" in 1975.

The release of "Star Wars" in 1977 brought Fox $235 million in domestic and foreign receipts, bosting its income from feature-film rentals 46 percent over the previous year. The success of the film also propelled the firm into an aggressive acquisition posture, precipitating the purchase of Coca-Cola Bottling Midwest and the merger with Aspen Skiing Corp.

Other studios reported similar success stories. In 1977, Columbia Pictures released "Close Encounters of the Third Kind," and its revenue from filmed entertainment that fiscal year jumped sharply from $298.3 million to $437 million for 1977/78.

In 1978, Paramount became the top film distributor when the Gulf & Western subsidiary released "Grease" and "Saturday Night Fever." The two films set box-office records, posting a total gross of $260 million for the year.

The heady financial achievements prompted a spending spree which, as in the case of Fox, extended beyond the motion picture arena. "Diversification Craze Seizes Bix," headlined a recent daily Variety, a trade publication.

The turnaround in the fortunes of the industry opened up the fiscal floodgates for picture production. And although the 1976 Tax Reform Act foreclosed further domestic tax-sheltered financing, which had been a major source of funding, the industry found itself well cushioned with high box-office receipts and strong credit.

Popular films also provided a strong opportunity for merchandising. "Star Wars," for example, which has earned about $467 million at the box office, has grossed another $500 million in sales of related merchandise.

Another boost for revenues produced by recent films has come from the sale of ancillary rights. "King Kiong" was purchased for four showings on NBC-TV for $19.5 million. Last year Metro-Goldwyn-Mayer Inc. licensed "Gone With the Wind" to CBS-TV -- 20 showings for 20 years for $35 million.

In addition there is a growing market for feature films in pay and cable television, syndication, videotape cassettes and discs.

How long will this trend toward production of high-cost films continue? For as long as they are successful, analysts agreed. CAPTION:

Graph, no caption, By John Pack for The Wahsington Post