I built a dolly this weekend using 2x4s. It took me about a day and a half working off and on... I saw a pic of one for a Laser I think, and figured I'd make one while I was waiting for my hull to dry out.
I'm guessing it cost me about $50 to make it. The wheels were about $7 at Harbor Freight and the rest (wood, screws, etc) came from Lowes.