In Holland you get an iPhone with a TMobile contract for almost nothing (depending on your plan).
You call TMobile after activating of the contract and buy off the simlock. That will set you back Euro 10,- for each of the first 12 months of your contract (so max Euro 120,-). Then your iPhone is legally unlocked and you can use it with a real network.
You sell your TMobile contract with unlimited internet with 25% discount to someone else.
Total cost at worst possible conditions Euro 450,-:
- Setup contract, including iPhone: Euro 150,-
- Unlock: Euro 120,-
- 25% discount over 24 months: Euro 180,-
It can be less if you take a different contract and pay less on setup (free phone) and are able to transfer your subscription with less 'penalty' to someone else.
The unlock proces is smoothly, but TMobile isn't very co-operative. In Dutch only: