I'd rather have Tek at that cost, then some other FA.
Tek isn't stupid. If he wants to come back to Boston, it will have to be at the rate the Sox want to pay him, and he will have realize that if he comes back theres a good chance he will be mentoring his eventual replacement and splitting time with said person. It's up to Tek to be able to embrace this or not.
If Tek making that much money troubles you, think of it this way, Salty won't be making much. Think of it as having 2 C's making 4-5M each, instead of just one making 8-10MM, LOL.