They need to I pliment jewels directly into the game so people playing must continuesly purchase them to keep playing or simply sell what they find in game. Everything in game should use jewels not in game currency or at least trades between players or auction house should be done with jelwels.
That would mean that a person would have to pay a large subscription base. And in the end if JWL was used for everything ingame then where would be the value? it would end up being a closed system trading platform for jwl.
But I dont know :p