Gotta spend the money somewhere. Bradley's contract is hardly the crippling misstep its being made out to be.
You ARE going to spend the money, since if you're below the floor it simply gets distributed among existing contracts. However, in this case you have cap space -- and don't have an albatross of a contract.
I'm no GM but if given the choice between spending X dollars on 10 players and X dollars on 11 players, I would think having 11 players would be better even if the 11th is a marginal NBA talent (which Bradley is certainly more than).
Except that's not the choice. If you don't have Bradley, then you have the cap dollars to sign player 11 as your heart desires. What the Celtics brass is gambling on is that Bradley will develop and there won't be a better player they'll be able to sign with cap space.
It may or may not be a good gamble, but it's not a good contract at face value at this point.
Based on what sort of metric?
Considering the cost of veteran SGs this summer, that seems like a reasonable price. Throw in the fact that Bradley is a lot younger than a lot of the others that just got bought on the market, and thus still is considered to have a lot of "upside", I'm not sure I buy the argument that it's an overpay.
There is always "opportunity cost" with any transaction, but you have no way of asserting that there definitely would have been "a better player" that they could have purchased or traded for with that same salary or less. Since the probability is still hight that Danny will never even drop below the salary cap, you can't even really call it 'cap space'.
That kind of speculative hesitation is what keeps you from buying a perfectly good Ford Fusion that you know is a good deal with the money you have now, holding out hope that someone will magically sell you a brand new BMW 500series for the same money some time down the road. Sure, anything could happen, I suppose. But in the mean time, while that money is burning a hole in your pocket, someone else is driving that Fusion around.