Goes the opening line of the joke. The punch line is "because they're so worth it!"
I am assured by a couple of friends that this is gospel truth. I'll have to take their word for that.
Seems that housing generally has the same feature in that people have to pay quite a bit extra, per year to live in big cities. This makes sense since those councilmen, mayors, and commissions don't come cheap, no matter how little they actually do for you. The exception to this is Denver where living in the 'burbs seems to cost some $3,600/year more than living inside the Denver city limits.
I've lived in Denver, and I've lived in the 'burbs, and I tell you it's so worth it.