I own a 2010 Golf TDI and my girlfriend owns a 2005 Prius. I take care of and fuel both cars. The Golf gets an average of 42 mpg on diesel and she gets 47 ish on regular unleaded fuel. The new Prius costs now in the upper 20's and my fully loaded Golf was over $28k though I bought it used at a steep discount. As far as I know, there is no cost disparity for the benchmark Prius over the benchmark Golf/Jetta/Passat TDI. The Prius is more efficient around town by a good margin due to better mpg and much cheaper regular unleaded fuel. The Golf gets slightly better hwy mileage and is definitely superior to drive on trips but I keep it in the garage when I need to run around town since it takes 15-20 miles to warm up enough to break into the 40's. I drive my beater Focus 1.8T to go to work which is 1.5 miles away.
My opinion is that you buy a TDI if you commute over 20 miles and a Prius or Leaf if you are closer than 20 miles. I love TDI's obviously but I don't let it blind me to better tools for the job if you drive in very small hops. I cannot bring myself to cold start the Golf going to work when my Focus barely shows 100F coolant temp by the time I get to the office. I'm getting a Leaf in a couple of weeks for the 3-4 mile short trips me and my GF do on a daily basis. Whoever drives the most that day will drive the Leaf and the other will drive the Prius. The Golf will be for 20+ mile trips or special occasions.
And as far as Prius batteries are concerned, I can buy used ones for $300 all day long. Even if I get a "bad" used pack I can pick and choose from individual cells from both packs to make one good pack and put it back in. There are a ton of wrecked Prii since there are so many on the road.
I see it all the time the hating that is done on the Chevy Volt forum, the Nissan Leaf forum, TDIClub.com, etc when it comes to the other maker's car or propulsion type. Man, we should be together on efficiency and changing things. Who cares what efficient vehicle the other guy is driving? At least we're doing something different from most everyone else.
<off soap box>
Any dissenters? I'm all ears!