My biggest problem with Perk is that I think he is a GREAT center for a championship contender, where he can be a role player, surrounded with tremendously talented players. However, I think his value drops dramatically when he suddenly needs to be one of the top 2-3 players on the team...and I think paying him about $7-8 million per year makes it significantly more difficult to bring those other players in to put around him and Rondo.
I personally believe that anything above $8 million or so is star player money, when you are a rebuilding team. An team that is already built, can sometimes afford to overpay role players, because their core is already built, and they are not getting below the cap anyways. However, for a rebuilding team, cap flexibility is more important than role players. So they need to 100% sure they are signing the right players for the right amount of money, if they don't want to set their rebuilding plans back years at a time.
And unfortunately, I see the C's as being a rebuilding team in a couple years, and I don't think they will see a $11 million center, who is passable at best on offense (not to mention has a trick shoulder), as the smartest investment. Instead, I think they will decide to cut costs, and try to collect assets to hopefully find their next superstars to put around Rondo.