read the cricinfo article...yes seems he is a bit mixed up or he does not want to be seen turning his back on SA cricket. His salary from SA, would be dwarfed by IPL earnings, reading between the lines it seems he does not want to risk getting injured so he can play WC and IPL cricket. That's how I read it.
The quota system may or may not play a role it's hard to tell. Could they really leave him out if he was available for the NZ series?
I think sometimes you need to be a bit more honest. It's a poor state of affairs with any quota system but that may not be a real he wants to limit his time playing for SA in all formats.
it's a professional sport these days, players will earn as much as they can(look at chris gayle for example), there's nothing wrong with that and SA don't have the money to pay massive wages
what price playing for your Country is a good question.