How much does it cost to unlock an iPhone? - 1

4s

Normally $15 or so online. If you go to a local shop probably $35 or so. This would be to jailbreak it. If you mean SIM Unlock the prices are about the same. You can Jailbreak (Take ownership of the software) yourself without too much trouble. SIM Unlock (Change carriers on GSM) is harder and takes specialized software.

Depends, what carrier is the iPhone locked to?

Cost depends on iPhone locked network.

It depends on the carrier, some are very cheap like ATT ($12-$20) and some are very expensive like Rogers/Fido - $120+ . If you have an ATT locked iPhone, i highly recommend iPhoneUnlockedCheap.com they have great service.

I had the same problem as you as the jailbreak of my iPhone was being lost every time I updated my iPhone. I finally got it permanently factory unlocked at: http://www.iphonefort-mobile.com/ The unlock took a few hours for them to complete.