Justin
Looking at it from my standpoint I would say my overall expense (other than buying sleds) is equipment setup and entry fees. We both live in the 'banana belt' per say of all the races, so traveling expenses are relatively easy to take care of especially if you team up or stay in your own trailer. Everyone that would race would already have at least 1 sled that would work with little to no set up changes. If you want to go further than that it is up to you. Even with one sled though the costs can still add up quick. Belts, oil, carbides, clutching, traction, shock setup, etc... Some stuff you prob already have, other stuff you definitely need for racing.
I would point out that the issue of wrecking a sled every weekend isn't quite as prevalent as most people think. The only 'dangerous' hills IMO are Afton and Jackson for obvious reasons. Most the other hills are quite forgiving even if you have a major screw up.