"They'll get more out of you than if you'd pay full cost of an unlocked phone right away." That is some FAIL logic. Do they charge less for Data and Minutes and Texting on an unlocked phone? Looking at their plans it looks like they charge the same.
So on Sprint you would pay the full $500 for a Galaxy S2 phone, then pay $80 a month, while you could pay 1 cent and then $80 a month? And you think paying the $500 up front will save you money?
Nah you must think you can go to some cheap pay as you go wireless company after spending that $500 and then save a little each month, but in reality if the subsidy model went away Sprint, ATT, and Verizon would end those cheap pay and go companies using their networks. Causing those places to go under.
Then you'd end up back paying the same monthly rate to Sprint or ATT or Verizon, except now also paying the extra $300-400 up front, all just not to have a contract.