That's not arbitrage, neither is buying goods in one location and selling them in a far away location. Arbitrage is a simultaneous purchase/sale in different markets with a trivial amount of work and no risk. If there is risk, it's not arbitrage; if there is work, it's not arbitrage; if there is a lot of time involved (and thus, of course, risk), it's not arbitrage. Antique dealers buy from people who want to get rid of things and sell to people who want to buy things. They make a profit because historically it is difficult to find antiques when one wants to buy them. Even if you managed to be connected to every antique seller imaginable you'd have to be lucky enough to have an item go on sale within the time you want to buy it. Antique dealers serve as a buffer, offering quick cash to sellers and selection to buyers.