Many have done the cost break down of a <Insert Hybrid> vs. <Insert Gas Guzzler>. At the end of the day, you aren't going to break even on a Hummer (save for the obvious decrease in cost), let alone a G35. At the end of the day, what a Prius will do is help the environment, and in theory it would lower demand which could potentially lower prices (not gonna happen, but I can dream, can't I?). This will be even more so if the majority of your driving is highway. Full hybrids (capable running on just electricity) get worse mileage on the highway because they don't benefit from being able to shut down at stop lights, etc. Acceleration is also non-existent and therefore passing's a *****. A car like a Prius is great for city driving. If you are going to be doing a lot of highway driving, mild hybrids (like the out of production Honda Accord hybrid and some GM hybrids) are a better bet. They use electricity to assist the gas motor and by doing so increase performance and save fuel. These can't run on all electricity and as a result your fuel savings won't be as great as on a full hybrid. You will do better than your G35. though.