When Star Trek rebooted their film series in 2009, Chris Pine and Chris Hemsworth were mediocre famous. Hemsworth played George Kirk, James Tiberius Kirk's father, who dies aboard USS Kelvin while battling Nero. Pine played James Kirk, who's haunted by the death of the father he never met. After the film launched successfully, Pine went on to star in Wonder Woman and Hemsworth went on to become Thor. Both of those roles turned out to be career boosters for the actors, who immediately shot up Hollywood's A-list. 

Paramount Pictures was looking to reunite the two stars in Star Trek 4, and the plot was rumored to be a time-traveling adventure that would allow Kirk to go back and meet his father (or possibly send his father into the future). According to The Hollywood Reportersources close to Paramount are claiming that both the studio and the actors have walked away from the ongoing contract negotiations for the film. The sources say that Pine and Hemsworth were asking the studio to stick to their existing deals, which obviously place the actors in a very high price range. Both Pine and Hemsworth have had deals in place for the fourth film for years, but Paramount wants to renegotiate those contracts. Paramount was not willing to shell out the cash for their original proposal,  claiming that Star Trek doesn't have the widespread appeal of Marvel or Disney, so the budget would be much lower. Hemsworth and Pine have a price tag that they feel should be met, and were unwilling to take dramatic pay cuts, especially since the last Star Trek film was the lowest grossing movie in the rebooted franchise. Pine, who has starred in all three Star Trek films, will not be easy to replace.