Costco membership + sales-tax free states + anything on sale. People do this. Takes a lot of time I suspect, but there's money in arbitrage. Just remember: the

Costco membership + sales-tax free states + anything on sale. People do this. Takes a lot of time I suspect, but there's money in arbitrage. Just remember: the longer it's on the shelf, the more fees you pay. So yes, you may have found a great deal on something, but do you really expect to sell 500 in one year?