You can pay now or later. If you buy a phone on a plan you are going to pay the same price eventually. I am pretty sure the carriers are doing fairly well and it is not from giving away phones.
My next phone will probably be the touch diamond 2. If I could get it from rogers/fido they would force me into an additional data plan which I personally wouldn't want. I just use the wifi when I want data. When I get my next phone I will just pop in the sim card and continue on my current plan.
FWIW, Fido would love to sell me a new phone for cheap. The price of that would be the loss of my old City Fido plan. $45 month unlimited local voice, no system fee.
So if you don't buy the phone from the provider, are the monthly plans half the price - including data plans? I'm pretty sure none of the carriers are cutting huger deals for not using their phones, especially on data plans, so I don't see a lot of savings.
Scary thing about that site is that the iPoo and crackberry are on the low end of the price scale.