How do I manage an extremely difficult client without rage quitting?

I’ve been on this project for over a year now (was supposed to be done in 6 months) and the client has been insanely demanding with every single deliverable. We’ve had stuff go through V5, V6, you name it. I was originally the Analyst on this project and I think the PM was a little too collaborative from the outset, but I’ve recently taken over as PM as the original PM quit.

Right now we’re working on a short 6–7 page memo. We’ve already gone through multiple iterations and finally got it to a place where the main client contact was happy. Problem is she’s OOO and her boss took over, and he was unhappy with where it left of, so we redid it and finally got it to a good place (or so we thought). Then today I had a one-hour call where he basically tore it apart again. He even said, “I don’t know how much we pay you, but it’s probably a lot,” basically implying it wasn’t worth it.

I’ve never worked on a project where the client has been this difficult. We’re already about 30% over budget and I can see us ending up 70% over by the end as we still have a final report to do. We’ve tried managing expectations, but they’re never happy, so it’s been rough.

How do I manage this without burning out and rage quitting?