First the client is a prick. Do not deal with him in the future. On the other hand, if I were in your position, I'd just give up the files. It will save a lot

First the client is a prick. Do not deal with him in the future. On the other hand, if I were in your position, I'd just give up the files. It will save a lot of trouble and the client will not give bad review about you. Still, it will be your loss. But do not worry, other clients will come. You can sort of "adjust" your fees to cope up with the lost money from the previous client -- or just deal with it like a businessman and accept the loss (time and money). Think about the big picture. Is $150 (or even $500) worth it all?