J.J. Abrams' Star Trek came out 10 years ago this spring. It was not only a huge hit, spawning two sequels, it introduced Chris Hemsworth as George Kirk, father of Chris Pine's James T. Kirk. George was killed on his ship at the start of the movie, so that was the last we saw of him. Fast-forward to today, and Star Trek 4 was supposed to bring back both Chrises as both Kirks. That didn't happen, and the movie is now reportedly shelved.
The rumored reason for both Chrises dropping out was money, with both high profile superhero stars reportedly wanting more than what Paramount was willing to pay after the relative disappointment of Star Trek Beyond.
However, if you ask Chris Hemsworth, he turned down the next Star Trek sequel because he wasn't into the script and he's gotten more selective over time:
I didn’t feel like we landed on a reason to revisit that yet. I didn’t want to be underwhelmed by what I was going to bring to the table.
So Chris Hemsworth told Variety the fault was with the story/script/his role, not the budget. Maybe he didn't want to bring up money -- considering Forbes said he made $64.5 million last year. But he could've been honest about that and people would've understood his worth has gone way up since Star Trek. It's very possible the contract issues that made headlines weren't the full story and this note about the script is at the heart of things.
Back in 2016, Paramount officially announced Chris Hemsworth's return as George Kirk, saying the fourth movie in that franchise would be written by J.D. Payne and Patrick McKay. Here's what the studio said the movie would be about:
In the next installment of the epic space adventure, Chris Pine’s Captain Kirk will cross paths with a man he never had a chance to meet, but whose legacy has haunted him since the day he was born: his father. Chris Hemsworth, who appeared in 2009’s Star Trek, will return to the space saga as George Kirk to star alongside Pine.
On paper, I loved that idea. It's a way to get father and son together on screen, and also pair up two charismatic Chrises. But apparently something went wrong in the screenwriting phase, and/or Paramount wasn't willing to pay up after the under-performance of the third movie at the box office.
It's possible Chris Hemsworth was saying that if the story were stronger, he would've done Star Trek 4 for less money. Obviously he doesn't need the money. But if the script didn't impress him much and he was getting less than his usual amount? I can see him walking out. That's just speculation, but it would be a way to combine both the money reason -- which never came from either actor -- and the script reason coming from Hemsworth himself.