I disagree that a Sox GM needs to spend as much as every GM, and certainly not $50M more.
There are a few crazy spenders in MLB. Nobody should be expected to match them.
That being said, I do think he should spend up to the tax line, every year, at minimum. Going over, when it looks like you just need 2-3 key pieces makes a lot of sense, at least from time to time. Reset, when before you get to year 3 is fine with me.