Restrict the Gold Farmers Then
According to the internet:
Average cost of a 1 bedroom apartment away from a city center in China: $100 USD.
Cheapest rent I've seen in USA for a studio or 1 bedroom: $3-700.
Unless SE decides to restrict access to NA and EU servers for people with IP addresses originating in countries with incredibly cheaper costs of living like China, etc., gold farmers will "love u long time" as it were.
To them, investing $30 on a new account every time one gets banned is a great investment because a lot of these buyers are dropping enough in a single purchase to buy them a month's rent.
To SE, well heck, I put enough accounts on my blacklist in 1 day to account for about $275 (multiplied by 365 that's $100k USD per year) just on one server, in a small number of areas over the course of a few hours while I was in town to restock, etc. Multiplying that by the total number of servers, these gold spammers are giving them a lot of business; possibly millions per year or more.