That's not how the luxury tax works Jackson. The Red Sox would be paying 17.5% of the amount of money that they go over the luxury tax, because they haven't gone over the luxury tax in a while. The Yankees only pay 40% on the amount of money that they go over the luxury tax because they've been over the luxury tax every single year, and if you're over the luxury tax threshold 3 years in a row, you pay the maximum 40% penalty.
So if the Sox are over the luxury tax by 5 million in 2010, they'd pay an adittional $875,000, not the $5 million figure you just made up. Not nearly as big a deal as you're making it out to be. And they're shedding over $50 million in salary after this year, so they could easily go back under the luxury tax threshold.