ericinboston, i'm suggesting a slightly different thing, which would be raising money, yet not to buy computers, but instead to make marketing with it. Just the WCG message reaching people, it's mostly an auto-decision to say yes. Gather volunteers, and spend this money on the needed expenses like designing banners/posters, and printing them, and then you could re-sell them for cost, or distribute them.
If the 7500$ would get you 10 PCs for example, i believe if you spend them on marketing you could get 1000 PCs joining, not only 10. In addition maintenance, power consumption, and eventual ownership of the equipments would be distributed eventually. Which would only be fair for you and the doners.