You are correct, and I should have added that $15 - $20 air fills may be the result of that scenario, but it is still economics 101 that says ".....where there is a demand, there will be a supply....... and at a price that the market will bear......"
I agree that that compressor would still have additional costs associated with it, and I do admit i don't actually know what the true costs of running a compressor are, but those costs to the sporting good store would be, I think, a more marginal increase in that they are already paying staff and would only need to make a bit of an investment in training that existing staff on using it which could come from the money saved from buying the compressor cheaply for pennies on the dollar at the bankruptcy sale in the first place. I don't know how much more electricity it would use, but the point is that I think don't think it would be unworkable and you have to consider that added benefit of having that extra customer traffic through your store. Imagine that scuba diver coming in for his tank fill, notices the sale your having on bikes and buys one for their kid.