There's not a single franchise that can afford to keep all their talented players. Little thing called the salary cap. They've done a good job in keeping Stevie Johnson and Kyle Williams, gave Fred his money and made a mistake on Fitz. Jairus Byrd will most likely receive the next big contract.
For all Nix' faults, you can't say that he's been stingy in keeping the homegrown talent.
I hate to see Levitre walk, but if it means getting Byrd, Spiller and one more quality player on this team for years to come, then it was worth it.