Not terribly expensive. I use those little canisters for occasional plumbing and the cost is negligible. Having never tried brazing with one, I expect you`d use up quite a few over the course of a frame, so they`d add up, but that`s always the catch when you deal with "convenience" sizes of anything. For a single frame, MAPP would undoubtedly cost you less than tanks, regs, torch and tips for oxy/anything.