I don't know what it cost them, but my parents got a propane generator with a dedicated fusebox. They had a professional do the wiring and hookup. I think the way it works is that there's a main switchover breaker between the boxes, and a few circuits are hooked into the generator's box, to power things like the refrigerator, air conditioner, wood pellet furnace, and a few lights.
A substantial part of the motivation for that came in an ice storm a few years ago, which caused many trees and branches to take down power lines, leaving the power off for around 5 days. We did still have a standard wood stove at the time, so the house was kept warm and livable, though it smelled slightly of smoke, as the chimney was built very poorly, and has a lousy draft. Water for toilet flushing was provided by melting ample supplies of snow. 
So now they've got a nice big propane tank behind the house, and a fancy looking generator on the side of it.
Definitely do have this done by a professional though, since as Mark R said, this is a lot of power to be messing with, and you don't want to accidentally be feeding power back into the lines in the event of an outage. Utility workers don't much appreciate the whole death-by-electrocution thing.