$2 Million is not too much to pay when your stars are making so little. Tim, Tony and Manu took less so that the Spurs didn't have to roster moves due to financial constraints.
That said, as much as I like Joseph, he's certainly not untouchable. If the Spurs could trade him for a pick to use on Vasilije Micic, I'd consider that pretty good deal. Micic seems to have great potential as a play-maker and has the size to play both guard positions. He'd make a fine compliment to Mills and potential successor to Ginobili.