Do you have a Costco membership? They have pretty nice dog beds there (one of Nebo's is a costco bed) and there only around $20-$25. I've seen flat foam ones and they have also had round ones. Nebo has a few different beds and the one he likes the best is from Petco. It has a foam shape, I'm not sure how to really describe it....pics will work better.
Petco bed (I got it on clearance for around $20...I think it was normally $50-$60)

Costco bed