The news of the veteran action movie star's exit from the production emerged earlier this week, with Sylvester Stallone branding him "greedy and lazy" on Twitter.
And now The Hollywood Reporter claims that the Die Hard star's pay demands were the key issue - because he was apparently unhappy with $3m for four days' shooting in Bulgaria.
"He said he'd drop out unless he got $4 million," a source told THR. "A million dollars a day. Stallone and everybody else involved said no."
Stallone then apparently got in touch with Harrison Ford - who was happy to be drafted in.
The mole continued: "I think [Willis] was pretty surprised he was replaced in 72 hours by Harrison Ford — a better actor, a much nicer person and a more interesting direction for the film."
Willis' representative refused to comment for THR.
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