If you are true to your conservsationist values, you should look for decent parts at your co-op. That would be your first approach given what you have said here in the past. Second, if there is nthing wrong with your current crank set, why replace it? Just buy decent quality rings to get yourself into a good place again. It should not be a surprise at all that three rings purchased as individual parts are almost as expensive as a complete set. After all, the economies of scale of mass marketing products work that way. Have you ever priced out purchasing all of the components to build a complete bike and compared that to a similar level bike purchased complete with a warranty? You can't even come close.