The Big Bang Theory's five core cast members – Jim Parsons, Johnny Galecki, Kaley Cuoco, Kunal Nayyar and Simon Helberg – have agreed to a pay cut so their underpaid co-stars, Mayim Bialik and Melissa Rauch, can get a raise for the show's pending 11th and 12th seasons, Variety reports.

The hit show's five original cast members will see their $US1 million ($1.3 million) per episode paycheques drop $100,000 each, freeing up a $500,000 pot to be split amongst Bialik and Rauch for each episode.

Rauch and Bialik, who both became series regulars in 2010, currently earn $US200,000 ($261,000) per episode.

In recent seasons, they've seen their roles on the show expand, with Rauch's Bernadette having a baby with Helberg's Howard and Bialik's Amy becoming a popular romantic foil for Parsons' Sheldon. Bialik's picked up four Outstanding Supporting Actress Emmy nominations during her run on the show, too.

Following negotiations, the duo's pay packets could transform into about $US22 million ($29 million) each as part of the two-season, 48-episode deal, notes Variety.

Not a bad wage to memorise goofy lines about quantum physics and Star Trek characters, you might say, yet still dwarfed by their co-stars who've seen their salaries steadily balloon since the series debuted in 2007.

The crew's remaining $US900,000 ($1.2 million) per episode takes will still make them TV's highest-paid stars, with only recent deals from big-spending streaming services coming close.

Gilmore Girls stars Lauren Graham and Alexis Bledel picked up $US750,000 ($979,000) an episode each for their recent four-part reboot Gilmore Girls: A Year In The Life, a figure that Robert De Niro will also be claiming for Amazon's yet-untitled 20-episode project being produced by Oscar-nominated director David O. Russell.

Meryl Streep, meanwhile, is said to have signed up for $US825,000 ($1.1 million) per episode for JJ Abrams' upcoming Warner Bros miniseries, The Nix.

According to Variety, The Big Bang Theory has grossed over $US1 billion ($1.3 billion) in syndication fees for its production company Warner Bros, with an online streaming deal still to come as its TV exclusivity rights have just ended.

Warner Bros and the show's US network CBS also recently announced that a spin-off project, focusing on Sheldon's formative years as an adolescent prodigy, was in the works with Parsons on board as executive producer.

The hit sitcom's tenth season is currently airing on Nine.