IIRC, the producer, director, and at least one star (Christopher Lee, then of Hammer B-movie fame) all claim to have been paid nothing or virtually nothing for their work on The Wicker Man. In fact, that wonderful 1973 British detective story/horror/musical/religious melodrama/erotica/black comedy (yep, it’s all those!) appears to have been a labor of love for almost everyone connected with it, with the likely exception of the true lead actor, Edward Woodward, who loved the project but managed to get paid for it.
Then again, Woodward was the actor sitting in the hot seat.