Crowder should be untouchable. If Ainge wants to build a "sustainable" roster, Crowder is irreplaceable.
When you have the ability to add a guy who multi-time all defensive teamer who is averaging 24/6/5 then, I'm sorry, but Crowder is not untouchable.
There is nothing Crowder does that Butler doesn't do. And everything that they both do, Butler does better. Except maybe three point shooting, but Crowder didn't do that much better then Butler the previous few seasons.
Contracts matter too. Every team has a budget. The Celtics will not be able to afford Bradley, Smart, and IT after next season. They will be able to afford IT, Smart, and Crowder. Trading Crowder means this trade costs you both him and Bradley, and whatever else the Celtics are giving up. Unless you're down with something like Brooklyn 2017, Bradley, and Crowder to begin with, in which case we have an irreconcilable disagreement on Jimmy Butler's value.
You don't actually know this for a fact, you are just guessing.
Boston will have Bird Right's on all of these players, and thus can afford them if they are willing to pay the luxury tax bill.
I would be willing to bet Wyc is willing to pay it for at least a few years, until Boston starts to get hit with the repeater tax.
Whatever man. Keep living in happy fairy land where the Celtics are willing to pay $30 million a year in luxury tax bills. Even keeping Crowder, along with Smart, IT, Butler, and Horford, is very likely to send the team a few million over the tax line, and hit the team with a $5-10 million bill. Every dollar more that Bradley makes more than Crowder will cost the team about $2.50 in luxury tax. So when Crowder is scheduled to make $7.2 million in 2018, if Bradley gets $15.2 million (a perfectly reasonable number, if not arguably low), the Celtics will owe an extra $20 million in tax bills. And then the next summer, when Butler opts out and has his salary increase by another $12 million? That's easily an additional $30 million in tax bills, bringing the total to near $60 million.
That isn't sustainable, and the difference between Bradley and Crowder, in terms of long-term planning, is immense. A team with IT, Smart, Butler, Crowder, and Horford as the top 5 probably has a total luxury tax bill of $35 million over the next three seasons. Swapping in Bradley for Crowder is about $90 million over the same time. That's a lot of money, and I strongly suspect more than they're willing to pay to keep Bradley (considering I'm guessing he makes about $30 million over those final two seasons as well). In other words, $90 million to keep Bradley the extra two years that Crowder has on his contract.
Crowder is untouchable.