One of the more amusing ways to create a disincentive for goldfarmers, bots, and other fun things that come with real money transfers is to have unrestricted PvP (or nearly so). In EVE Online, for example, there are channels devoted to hunting down gold sellers and AFK miners, and good luck getting involved in the actual game part if half the server has you on its hit list as an eBay twink. If someone can kill you and take your stuff, you are less likely to buy stuff.
In Asheron’s Call, there is the classic story of a Darktide (PvP server) character sold on eBay, advertised as having three Mattekar Robes (are those still worth anything?). Let’s call him Bob. Bob told his friends he was selling the character and where he last logged off. Not long after the sale, “Your friend Bob has logged on.” While new Bob was getting his bearings, old Bob’s friend was traveling through portal space. Old Bob’s friend liked his new robe. Old Bob’s friends also knew which lifestone Bob used. Rough start on the new server, new Bob.
If that story is just an urban legend, please don’t disillusion me.