You can even get it free in US and Canada, but you also get married with the operator.
They have several different network types. GSM network is still a rarity and works only in big cities. Cell phones are usually assigned with the operator, I think. They don't usually have European type GSM phones with user changeable SIM cards (Here in Europe you can change operator by simply changing a stamp sized SIM card).
There are lots of tri-band GSM phones for sale in the U.S. I don't think it's correct to say that GSM networks are a rarity - with the almost complete merger of Cingular and AT&T Wireless, thier GSM network will have more customers than the biggest CDMA operator (VerizonWireless). Without a doubt, though, a lot of the handset cost is subsidized by the operator - meaning that they'll lock you into a one- or two-year contract in order to get the good price.
The only fear of buying a GSM handset from the U.S. is if it has been locked by the operator - the same thing that is now being done in Europe on occasion. It's best to verify that the phone is unlocked, or see if it can be easily unlocked (which might void the warranty).
My suggestion is to buy a handset from eBay. I don't think you'll beat the prices anywhere - especially if you're OK with a used handset. Again, make sure the phone isn't locked or can be easily unlocked.