Its definitely not as big as Runescape is, most things that you end up buying with gold you can live without (flashy gear, mounts, toys) but there are some items in the game that people don't want to grind for so they will fork up the cash.
Nice thing about all the other games I bot on is that you don't really have to worry about being banned, I've botted on wow for about five years and have only gotten a suspension within that time frame. So its not a huge risk to farm in them.
I used to play that game so much in High school spent sooo much money until I realized that its not even that fun.