Technically it's their client that's putting the thumb screws to them.

If that's the case the logical solution is to put your commercial hat on and find another client. Amazon aren't the only ones paying.

If Amazon was your only client that'll be tough, but speaking from experience if you don't diversify your client base, you're living on borrowed time anyway.

This doesn't mean Amazon are not being abusive, but the solution isn't to moan on the internet.