You are right about the cost trade off and since this is specifically about MPG that's a big deal. Even that has trade offs even if there is an improvement. Improvement around town? Improvement on the freeway? Improvement in both but mostly in one? None at all? I suspect that improvement would be mostly in stop light to stop light driving. That's a pretty easy calculation to determine if it's worth it or not.
Getting into possible performance benefits and question becomes tougher. That's not generally about the money.
Part of the problem I think is in Ford's own sloppy use of the term "performance". I mean, really, what does that mean? Higher torque at the given RPM? Higher or equal torque in a lower RPM? Higher torque across range?
...or are they equating performance with MPG? Or both?
A rather weasely word on Ford's part.