People of the UK! iPhone Question...

Hey guys, i was just looking through all the tariffs websites and i made a strange discovery.

Last year when i purchased my iPhone 5 it cost £10 with a £37 monthly fee*

Now... The next generation phone the iPhone 5s costs £119 with a £37 monthly fee*

*All using the O2 network

shouldn't the old price of the iPhone 5 be the new price of the 5s? it doesn't make any sense to me... Am i missing anything here?