I did some simple math on that too.
At 12,000 miles/year, about my typical, I might only have to buy 300 gallons vs 400. I say "might" because I'm not sure hybrids save as much for the mountain driving I do. But let's say it does save me 100 gallons a year. At $2/gallon, it takes 4 years to pay back. That doesn't account for spending that $800 up front vs. buying more gas over time.
It's also true that over the last 10 years gas has been well over $2 much of that time https://www.gasbuddy.com/Charts , and I'd guess it'll be more than that again for much of the next 5-10 years.
What about repairs? Am I more likely to have more repairs on a hybrid, replacing battery packs or whatever else with that system? Any fewer repairs on brakes or anything like that?
Better resale value? Or are people leery about buying older hybrids, due to potential battery life issues, real or otherwise?
Non-economic factors? Stopping for gas less often is a plus. So is being quieter in electric mode.
Is it greener? Certainly burning less gas is, but what is the environmental cost to produce and eventually dispose of the batteries?
Lots of questions for a "no brainer!" $800 is less than I figured it'd be, but I'd want the answers to those questions before buying, if I decided a RAV4 was for me and just needed to decide hybrid or not.