It's not that strange for regular players to sell gold either, and often times doesn't require a huge time commitment. Final Fantasy XI was a prime example. Veterans of the HNM scene (end-game) or high level crafters could make tens (or hundreds) of millions of gil every day, and with most of the very best buyable equipment/expenses topping out at around 100-200 million, you ended up with a lot of excess money after a while.
Around 2005 or so I believe it was something like $75-100 per million gil, $25 or so in 2009 when I quit. People selling a couple hundred million every few weeks or in a month, wouldn't even have to work a regular job (though, most of the folks I knew personally did). I bought and sold a few times, but never made it a regular thing. When I quit I sold everything and probably made back all the money I spent on subscription fees over the ~5 years I spent playing.
Would wanna do it as punishment in prison though. Or even be in prison.