You can argue that about any limited resource for which firms are in competition, like land. Unlike most resources though, Google ads take into account a quali

You can argue that about any limited resource for which firms are in competition, like land. Unlike most resources though, Google ads take into account a quality score, so if one of those merchants is lower quality than the rest e.g. users go back from the store to keep searching more often, then they'll have to pay more and all other things being equal, the more useful merchants will outcompete them. In practice AdWords does enable many businesses that would otherwise find it too hard to reach a niche audience, and wouldn't be able to rank organically for a keyword because they have no inbound links.