You sure? The Volt is a piece of sh*t when running on gas. It requires premium and gets 35 mpg. It was always sold as an electric vehicle with extended gas range because you do not want to run it on gas (due to its inefficiency). The Prius is simply a plug-in.
This number is about where most people thought Toyota would settle. GM can now finally stop pretending. The Volt is damn near dead in the water. Its sales are a completely catastrophe this year and unless it pulls a rabbit in Q4 its 10k sales estimate will be squashed.
This Prius vs a Volt:
1) 5 seats instead of 4 - Kind of, you may get 3 kids in the back seat but there's no way 3 adults are going to fit well.
2) Toyota quality - Look at the comparisons done on quality lately, Toyota's quality isn't the selling point it used to be.
3) MUCH cheaper to run on gasoline once battery runs out (50 mpg vs 35 on cheaper fuel) - If you're planning on driving regularly it for long distances on gas the volt was not designed for you. It's made for the majority of people who drive 40 miles or less on a typical day but sometimes drive longer distances.
4) $10k cheaper purchase price - Sure, if you don't count the tax credits. If you do it's only about $3k more for the volt.
5) Shorter range on electric (though also more practical on standard electrical outlets, too) - So you're pretty much guaranteed to use some gas every day, whereas the majority of people would use no gas with the volt on a typical day.
I'm unclear now on whether this qualifies for tax credits, but it should to some degree.
EDIT: It appears $2500 tax credit applies, so $29,500 for this car. You'll be unlikely to make money back any time soon vs a normal Prius but this isn't that bad, you're looking at $5-6k over the regular prius to be able to plug it in. Looks like it actually drops 1 mpg in combined driving when the battery charge is up.
EDIT: Base also has nav, so the plug in is a pretty small premium in cost.