By any measure, “The Big Bang Theory” is one of TV’s most valuable shows. But it is not immune to the law of diminishing returns, and that simple fact of business physics will sway the upcoming contract negotiations for the show’s stars as the “Big Bang” stakeholders look to next season and beyond.

The deals for the program’s key cast members are up after this season, the show’s 10th on CBS. Jim Parsons, Johnny Galecki, and Kaley Cuoco are already TV’s highest-paid comedy actors. The trio reached the $1 million-per-episode mark (at 24 episodes per season) in their last three-year pact with Warner Bros. TV. That deal came in 2014, after a brief public tussle that emerged as production began that summer.

Two years later, “Big Bang” is still pulling in big audiences for CBS (the season 10 premiere grabbed 21.5 million viewers) and huge dollars in syndication. But that doesn’t mean the threesome will be able to command huge raises to sign on for more years.

“Big Bang” has generated well north of $1 billion in syndication revenue since its off-network debut in 2011. But those lucrative sales to local TV stations and cabler TBS had clauses that capped the buyers’ length of commitment. That’s common practice even for “Big Bang”-size hits in order to protect purchasers from being on the hook for an open-ended deal at top dollar. The cap is believed to be set at eight seasons for the stations and 10 seasons for TBS.

By the close of season nine, “Big Bang” had racked up 211 episodes. That’s enough for stations to run episodes as frequently as five times a week without repeating any for nearly 11 months. Warner Bros. already negotiated new deals with station buyers for the new episodes beyond season eight; the agreements don’t add significant dollars for the newer episodes. Talks with TBS are coming up. As strong as “Big Bang” has been in syndication, TBS is unlikely to commit the same high fees to secure a few dozen later episodes as it did for the first nine or 10 seasons.

Meanwhile, the cost of producing “Big Bang” has skyrocketed to around $9 million an episode — more than half of which is actor salaries. Supporting cast members Simon Helberg and Kunal Nayyar have seen their paychecks climb to around $900,000 per episode this season, the last on the current deal.

Warner Bros. TV’s license agreement with CBS calls for the network to cover all production costs plus a slight premium. That doesn’t give Warner Bros. TV the biggest financial incentive to produce new episodes, although there are other considerations. For one, there are the bragging rights of having TV’s top-rated comedy. For another, there’s the studio’s relationship with “Big Bang” co-creator/exec producer Chuck Lorre.

CBS’ deal with Warner Bros. TV for the show is also up after this season. As much as the network’s rivals covet the ratings of “Big Bang,” it would be a huge financial stretch for a rival net to offer significantly more than $10 million an episode to persuade Warner Bros. to move the show.

The high cost already limits CBS’ upside on the show, which last season fetched about $350,000 per 30-second spot (there are about 16 in each episode). Again, CBS realizes other benefits from having “Big Bang” on its air that make it worth the price tag — from serving as a launch pad for other shows to packaging its spots with other programs for maximum leverage with advertisers. But the license fee can’t get too much higher, or the financials just won’t work.

The “Big Bang” core trio achieved small profit-participation stakes in the last negotiation — a big win that’s akin to a lifetime annuity (assuming Hollywood accounting stays in check). Sources close to the situation say there is no discussion of the studio putting more points, or even fractional points, on the table for the actors.

All of which means that a new deal for Parsons, Galecki, and Cuoco will likely be similar in value to the last go-round. Sources close to the situation emphasize that at this point in the show’s history, the spirit among the stars is so strong that the incentive to strike a new deal will be less about securing a huge raise and more about protecting the show’s legacy in what is expected to be its final seasons. But even if their wages are stagnant, the math still looks pretty good for America’s favorite geeks.