Well, okay, that's a bit misleading. For one thing, the only place I'm aware of that being mentioned was in regards to Return of the Jedi, where his salary was to include net profits for that film as residuals (source), not that the residuals were his entire promised salary or that he never got a dime for playing Vader, which almost certainly isn't true.
Still, sad to see him passing, 2020 is claiming it's last few victims.
Edit:
Ok, that's also misleading past a certain point. The reason that Prowse was banned was never made openly public, even I believe by Prowse who only stated that he burned too many bridges. Tying it to complaints about not being paid is speculative at best.
Can we mourn the man without tossing around accusations like that?