Customer constantly requesting revisions

[gligor02]

Okay, so I have the problem with one customer and really don't know what should I do in this situation. Couple of times I have delivered the finished work, each time he requests revision immediatly and writes "Thanks for the delivery, I will check it soon". Then each time I have waited long, long time to get the feedback and when he comes back, he writes me "I checked it, but my artist figured out he made some mistakes, he will have to update the art and you need to redo everything again". Two times I tolerated this, but third time, I have waited two weeks on the feedback just to get the messege: "Designer figured out he positioned layers badly, we will fix it and send you new files".
I told him that fixing this will require additional payment, because again it is not my issue at all. He said: "Either you will fix it, or you can cancel the order because we cannot pay the additional amout you requested".
 

I have literally done the whole job, and did 2 revisions that were included, and I don't want to cancel the order just because he can't pay additional work, what should I do in this situation?