Movie ticket prices have long been a subject of grumbling among theater-goers, who have balked (but paid) for years as admissions rose ever higher into the double digits. But as two of Hollywood's leading directors recently noted in a panel discussion, it's likely to get a lot worse -- and ultimately will change the industry forever.

"There's eventually going to be an implosion -- or a big meltdown," said Steven Spielberg, who sat down with George Lucas at the USC School of Cinematic Arts on Wednesday. The conversation was originally reported on by The Hollywood Reporter. "There's going to be an implosion where three or four or maybe even a half-dozen megabudget movies are going to go crashing into the ground, and that's going to change the paradigm."

Big budget films like last year's "John Carter" or this week's "Man of Steel" have bumped budgets into the hundreds of millions, and Spielberg suggested that once more than a handful of them flop at the box office, the industry will be forever altered. He said that theaters will start charging different prices for different films -- like $25 for "Iron Man" or $7 for a smaller film like his own "Lincoln." (Which, he noted, came "this close" to being an HBO movie instead of a film in theaters.

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That's already happening -- Paramount and Regal Theaters have paired up to create a "Mega Ticket" for the upcoming Brad Pitt film "World War Z."

George Lucas agreed with Spielberg, with whom he has paired in the past on multiple films. Lucas suggested that attending movies in the theater is going to become more like going to Broadway, with fewer movies released that stay there for a year or more, with higher ticket prices.

But why do movies cost so much to make? Part of it is that blockbusters require an A-list star like Tom Cruise, who can cost upward of $75 million to hire. But another part -- as Lucas noted -- is that marketing budgets are enormous. Those high costs paired together mean that movies are geared to the masses, rather than to niche audiences the way TV shows are; he called cable TV "much more adventurous" than film today.

Still, those aren't the only factors involved. As New York movie critic David Edelstein noted in his "Man of Steel" review, quoting from producer Lynda Obst's book "Sleepless in Hollywood," big-budget, action-heavy films now help studios recoup more than 80 percent of their profits from overseas sales -- especially in China. Explosions, car chases and action require less translation and cross cultural borders, which means theatergoers in the U.S. should expect even more (and it may explain the last 45 minutes of "Steel").

Meanwhile, actors (like Zach Braff, who held his own Kickstarter to raise funds for a new film recently) and directors alike are recognizing that the best way to do projects they really want is to create them from scratch. Spielberg noted that the only way he got "Lincoln" into theaters was to co-own his own studio.

"The pathway to get into theaters is really getting smaller and smaller," said Lucas.