I'm not sure quite what differences in demographics would have to do with it. It seems to me that liking to buy things for as cheaply as possible, and also wanting to buy other things in order to save time, are pretty universal traits.
I'm not quite sure what your point is. Could you please restate it?
The only reason why goldmining is banned on World of Warcraft, whereas, in effect, it is allowed on Farmville is because goldmining poses a direct threat to Blizzard's revenue model, while on Farmville the producers have essentially become the goldminers themselves; Farmville's model is goldmining.