Just wait a few weeks, Golden Saucer will put the majority of them out of business.

It's supposed to have a gambling-like aspect to it. While you won't be able to win gil with it, as it's been said that GS will use a currency that cannot be converted back into gil, I'm sure that the Saucer will have some very tempting exclusives that can't be obtained elsewhere and a few that will be extremely difficult to win.

The effect will be like a "steam sale" for your in-game wallet, I'm sure, come 2.5 patch #2 nobody will have the money to play the player-run casinos anymore. Gil vacuum machine, activate!