I'm sure money is part of it, but in my opinion, it's more about bandwidth. The Pac 12 is wanting carriage of 7 channels, that only a very very small percentage of Dish customers are going to view. You already have people clamoring for 24/7 HD RSN's, Fearnet, AMC, YES, the missing Disney HD channels, etc.. The best I can see happening is Dish carrying the main Pac 12 channel, but I doubt the Pac 12 wants to allow that.
If the Pac 12 Nets are going to be important viewing to you, then wait and see if Directv or your local cable company gets it and then change providers. The market is so over saturated with channels now, I just do not see any one provider carrying everything in the future.