Yes, I get it and I am looking at it that way, too.
They paid most of the contract, so they should pay most of the taxes. I just don't think this way is proportional.
The contract was $83M. Let's say they pay the Sox $27.7M, which is 2/3 of the total contract. In my opinion, they should pay 2/3 of the remaining tax hit, so at the end of his deal, they pay 2/3 his contract and 2/3 his taxes, since AAV is what is used to calculate the taxes.
2/3 of the $13.8 lux tax cost is about $8.6M. We'd be "on the hook" for $5.2M not $3.8M. The difference is not much, but I think it is fairer.