You know, the -design- of the Prius et. al. was -not- to have it "pay for itself". This isn't surprising. My household refrigerator and washing machine don't "pay for themselves" either.
The Prius was tuned for -emissions- -efficency- not mileage. I knew this. For instance, in climbing hills the gasolene engine goes -much- faster than a comprable non-hybrid sedan. The higher speed is turned into electricty and then back into torque. If I punch it on the hill the engine goes faster still. The rule of losses in the transformation of energy dictates that energy (mileage) will be lost to transformation. Entropy must be paid. But the whole thing is squeaky clean.
People who expected to "make money" on their 40k car were idiots buying for the wrong reason. The rest of us bought for the green, and the smug, (be honest, there is smug to be had. 8-) and to drive down the price points as earily adopters.
And "mileage" is nearly the worst measurement of efficency there possibly could be. It is no wonder that big flat florida has people who -are- making back their money. The state is -flat-. If my commute were flat it would my mileage would be much better than it is today (42mpg). I have gotten 55mpg driving from Seattle to Portland, and only 48 driving the other direction (the sawtooth patern of the hills along I-5 is a determinant, very helpful going south, somewhat wasteful going north).
I lose most of my "mileage" in a prius in that once the engine starts it wants to run till it has "warmed up", which takes a significant part of my commute and is concentrated in the stationary time while I am stuck in surface street at terrible traffic lights, trying to get onto the highway. This meanst that all of my gas is spent pointlessly making heat.
I will likely not buy another hybrid though. I am planning on going electric next (e.g. leaf). Or to a Volt-Alike hybrid if I must.
Further on, I don't expect the electric to be much cheaper to run than the Prius. The state of Washington is gonny slap on a GPS tax any day, and electricty is clean but it aint as cheap as you might think. Ask anybody with an elevator or regularly used winch in a space they pay for. But I can aford the hit. I like having the smug, and I like having the cleaner tailpipe in general. -Someone- has to start paying to break the oil addiciton and having that opinion without willing to back it with my wallet would be hypocritical.
Full Disclosure: I also am midst of installing a geothermal heat pump in my house. I am expecting some savings, and some resale value improvement, but I doubt it will "pay for itself" for a very long time if ever. I'd like to back it with solar pannels because if I can get my energy bill down I expect to be able to sell the flash of having a negative electric bill several times a year when I sell the house.