You probably shouldn't try claiming "consequences" for underprivileged third world workers into this, considering that most of the Western economy is based in part off those same workers being exploited for all sorts of things. Shoes, clothes, chemicals, minerals, home entertainment devices, etc. So drawing a line at gold farming in a game....seems a bit silly as the reason why people shouldn't do it. To put it another way, if you are so worried about the plight of abused workers overseas with regards to gold farming, you should probably get rid of your phone, your computer, your television, your car, your clothing, and probably most of your household appliances. Virtually all of it has, at some stage of production, those same workers behind it.
The wider issue is that games give you an option of spending time to get the various perks via credits. People who don't have (or don't want to spend) that time therefore exchange money to bypass that particular sink. Game companies don't view this as a problem at all actually, if they are the ones making the money off of people exchanging that money for time. The real issue is that games have problems with other companies essentially taking profit away from them in their own game. The issue has a lot of different resolutions to it, not simply banning the exchange of goods and money between players. There are numerous safeguards that other games that have equivalent grinds where credits are the be all and end all have introduced that work fine.
