The variance you are exploiting in this arbitrage setup is a result of the inherent variance in information about the chairs, i.e. uncertainty. Since they are used, there is lemon's principle at work. You can argue that Aeron's don't really depreciate in quality that much though over time so that variance in unjustified and in fact there should be some exact market price (perhaps as a function of time used, or more simply just dependent whether its used or new). But the thing is, more likely than not, that variance IS justified. Some of the chairs may be less broken than others. Some of the sellers may be less dependable than others. You can of course condition on this stuff - pick the low price chairs and mark them up by being the most dependable supplier, vouch for the chairs, become an expert in the chairs and be better at out the lemon's, but those things all add cost, so NOT doing all that work is already priced into the market. But cool experiment nonetheless! I have also found that I can buy a used Aeron, use it for a few years, and sell it back for like the same price. Not really a quickly depreciating asset .... maybe better than the stock market the last few years ...