My thoughts would be that most people pay for their phone as part of their monthly bill rather than up-front. If Apple knock the price up by $100-$200 over a 3 year term thats only an extra $3-$5 a month the customer is paying. Their carrier might have lowered their data plan prices by then too so the customer doesn’t even notice the increase.

It’s not great that their prices rise but most people aren’t paying $1300 in one go for their phone.