Andy, but this isn't exactly like a job for these guys. It's not flipping burgers at McDonalds 40 hours a week. And the GCL/NYPL/SAL/FSL sure isn't making money on the backs of these guys. Many of these games draw crowds in the low hundreds, even with comp tickets. As I've said upthread, the players are investing in possible future careers with their time in exchange for coaching, training, nutrition advice, meals, equipment, uniforms, competition opportunity, cheap rooms, off-season contacts, etc.
It really is OK to pay entry-level workers sub-minimum wage, and that is true under the most liberalized minimum wage laws in the US, if they are receiving current or future non-monetary compensation. It's also "true" under common sense.
The clubs could CHOOSE to pay players in the lower minors more, but I'm certainly not horrified by it, I don't find it corrupt, I don't find it appalling, I don't think it's an outrage, or any of the other epithetic comments made by other posters. It's a voluntary transaction between the player and the clubs. SF makes a good point that the near-monopoly status of MLB means it deserves closer scrutiny, but I think it passes any kind of scrutiny. As I've said repeatedly, the key for passing that scrutiny is current or future non-monetary compensation.