I didn't want one. After carrying one for work for too long, and taking entirely too many 2am "emergency" work calls .... I didn't want one. Frankly, there aren't that many people I particularly want to talk with, anyway.
However, I wanted the convenience. Handy to have one when I'm travelling, and so on. So, I got a "pay as you go" deal thru AT&T. Just a phone, nothing else (no email, web browser, games, etc etc etc), that I can talk on for 10c / min. I pay $25 every three months, and the money rolls over, so it's not a use it or lose it type deal. There are other plans, too. The 25 dollar one is just the most convenient for me.
To me, that 8 bucks and change a month is worth it, like when my kid broke his arm, and I needed to co-ordinate which hospital to go to on the fly with my wife. Handy as heck, paid for itself for the year, right there.
Your mileage may vary. But I thought it was worth mentioning.
And you're absolutely right on the cost. My sister-in-law pays $100+ / month for hers. She says "My entire life is on it" ... but to me, it just looks like an expensive toy. Especially, since I've not missed all of the whizbangs that my old cell phone had, not one bit.
Audiobooks, news, freerepublic and GPS. Other than that I could do without a phone.