Not to blatantly fuel the fire, but I think it's kind of silly to want increased fuel economy for strictly economical reasons. Granted, we live in a society that's more or less run on petroleum. That being said, I think it's totally worth while (assuming you're able) to maximize your fuel efficiency.
Not only for saving money directly at the pump, but also for lessening the environmental impact as well as reducing dependencies on foreign (or any) oil. I think it would be awesome if one day we're all driving around in electric vehicles, or better yet, if public transportation was able to accommodate us to the degree that we no longer depended on cars to the degree we do. I live in the next city north from Portland, OR and the powers that be sound like they're looking to (finally!) extend light-rail here.
I guess the point is that if you drop x number of dollars on mods in increase your MPG, there's *more* than just the direct savings on gas to consider.
Speaking of which, I took my 06 GP on my first longer trip this last weekend, a little over 100 miles each way - unless I did my math wrong, I was only getting around 23-24 highway! Yikes! I've only had the car for two or three weeks - but I gotta figure this out. No mods yet, though.