Well some people sell 100s/ day but I'm pretty sure the method most people are using is illegal and if they aren't using it directly their sellers are. Considering RSGP is around .40/mil a $6 upgrade (not sure about prices) would have to be 15mil to break even. If the company was to charge back the phone bill then all those people who get upgrades sold to them would be in negative credit, so there is potentially a big risk with doing business this way.