Or, you could compare the Terrafugia to a two-seat LSA. That would be a fairer comparison, since the Transition is an LSA while the 172 is a real certified airplane. Pipistrel and Icon both sell LSAs for about half the price of a Transition.
There's no reason to only examine new aircraft, but even if you insist on that, you can do vastly better. For example, a Pipistrel Sinus will set you back about $86,000:
http://www.aviationbull.com/sinus
Compared to the Terrafugia, you can buy that, plus two $30,000 cars, and still have $133,000 left over to rent more cars. Or, say, buy a house. The Sinus also carries more weight, flies faster, burns less fuel, has a better range, and requires vastly less runway.
It's also probably substantially safer in the event of an engine failure. I don't see a glide ratio listed for the Transition, but just from looking at its relatively large frontal area, low-aspect-ratio wings, and gigantic road-sized front wheels exposed to the air with naked struts, I'd guess it's probably in the Cessna range of 10 or under. The Sinus has a glide ratio of 27, meaning you can get quite far to an airport if the engine quits. It's actually a decently performing glider in addition to a regular airplane.
If you expand the search to used aircraft, you can get quite cheap. For example, Cessna 152s in decent shape can be had for under $40,000, and that's not even the cheapest option.
Terrafugia Transition, new: $279,000
Cessna 172 Skyhawk, new: $289,500
The Transition only seats two while the 172 seats four, but I'd personally rather have the plane that also drives.
http://www.terrafugia.com/aircraft/transitionR
http://www.cessna.com/single-engine/skyhawk