Can someone please explain the advantage of a SIM unlocked phone?

Ok, you pay $700 for the phone (v.s. $200) and pay the same for data and voice.

What is the advantage?

I realize that you CAN opt for a cheaper plan, but in the long run, the two kinda equal out (because it is subsidized) but with the locked phone you get a better plan.

What is the minimum "iPhone" plan compared to the minimum plan. If it is only 15 dollars a month difference (say $30 vs $15), 24 months = $360.

So a 32GB iPhone is really approximately $1020.
And a n97 is $700 + $15 * 24 = $1060.

So you get a (theoretically) worse plan, have to pay more upfront (or buy on credit), and what for?