Not sure what he is worth, but any asset we gain can be used to acquire someone better with a higher salary. Right now Hauser gets in the way of using much of our trade exception for Anfernee Simons. Moving him for just draft assets would let us turn around and find a different player who make up to around $24 million, including acquiring that player in a sign-and-trade, while staying under the tax. Moving him is the best way to add a true starter-caliber player without taking a wrecking ball to our core (which I understand some want to do and you may or may not be right, but this would be the least disruptive set of moves that creates a noticeable improvement).
No disrespect to Sam, because I think he is a quality NBA player who provides value relative to his contract, but it is difficult to see the Celtics improving substantially without him being moved. His salary gets in the way of the TPE, or is otherwise useful to combine with White to add a star-level salary, and there is no one else in his salary range on the team.
I just want to clear something up since there has been some confusion around how much space under the tax we actually have.
As it stands, Spotrac says that we are $13.2M under the tax, which adds up to what you have above (Hauser at $10.8M plus $13.2M equals $24M. That sounds correct if we use our TPE, but if we were to use the MLE, we should be able to spend the entire $15M, correct? All 14 of our salary slots are currently 'filled' (yet not guaranteed), so if we dropped Shulga and his $2.1M, that should presumably give us $15.3M in space to spend on his replacement.
We also will likely have several minimum players and we saw how Brad essentially dumped three of them at this last deadline to cut even more salary. Doing that would allow us to basically use the entire TPE or part of the TPE and part of the MLE.
I don't want Myles Turner, but I believe there's a world where we trade Hauser into cap space, take Turner ($26.5M) into our TPE, and then we still basically have taxpayer MLE level money (projected $6M) for another player if we trade three minimums at the deadline to just get under the tax. Banton, Harper, and Williams make a combined $7.5M.
In short, I agree with you that trading Hauser makes sense if there's a deal out there for him. Especially since we have some young wings hopefully ready to take the next step (or at least one of them ready to take Hauser's spot). It also could create some much needed depth at other positions of need.