So what is the connects on over inflating tires?

I was inflating my tires to max sidewall (51 PSI) for a couple months, recently I brought it back down to the recommended PSI of 32 after seeing quite a bit of wear on the middle of the tire, I feel like my MPG dropped by a couple percent. I was wondering if anyone has done the math on how much over inflating tires saves on gas versus the increase cost in replacing tires sooner?