I think $10-30 is about right for the highly neglected bikes you usually find at those places. I've never flipped bikes, but I've flipped cars & the recipe is about the same, I would guess. If you know what you're doing, you buy the $25 bike, put the LBS equivalent of $200 of work into it & sell it for $125 or something, right? Well, the general value of the bike, imho, in it's thrift store state, should be estimated as the resale value in working order (+/- depending on cosmetics like paint condition) less the market value of hiring the work (at a LBS) to get it in that condition. I don't see why the thrift store should collect more...or why they should bother, for that matter. The hypothetical $25 for rolling it from the back door onto the floor & putting a price on it is much more profitable work than the hypothetical $100 for restoring it into a functional state.