I don't know why we're expected to spend so much on bedding sets for babies, anyway; they're not supposed to have the quilts on them anyway (because of the risk of suffocation) or even the bumper pads when they start rolling over/ are able to use them to climb out of the crib.
We got everything used. Granted, we've never had a really cohesive decor plan for Simon's room, but I found great crib sheets in primary colours, polka dots, gingham fabrics, solids... He doesn't seem to mind the variety, and I could afford to get a ton of spare wheets for my "heavy wetter".