last time i did the maths the cost of 24 month contract on an iphone vs purchase outright and sim only (like for like deals) was pretty much the same over 2 years (give or take a few quid).Never understand people buying phones for their full price. I have always found contracts to be cheaper. You pay monthly for the phone, minutes, texts and internet where if you just buy the phone than you have to pay for a service for it too.
After 12 months, the phone becomes yours and you can upgrade to a new one while you sell the old one.
these days with a purchased outright OP3 and £18 sim only im quids in.