Don't forget the various machine shop, powder coating, anodizing, ect. services that you don't have to account for on the BoM. On bots where most or all of the frame is custom made and made pretty, the cost for those services can be pretty substantial without a sponsorship. Plus, some designs might require special tools to be purchased or made that can even more to that number.
Also, I agree with Gray; if I'm not losing sleep, I'm not at the workshop enough
