I think a lot of the importance of the Volt is improving the public's perception of GM as a whole. As a green company using cutting edge technology...
Toyota (prior to their current issues

) was perceived as being a green company because of the Prius, but they sell monster sized vehicles too...
I personally think that if you're looking at $ savings only going with a Cruze is the way to go, but just looking at $ a Prius wasn't the best choice for people...they made that choice to save the Earth lol and then looked down on the rest of us