Assuming you are on a plan where there is just a monthly hardware surcharge, you likely pay 20% of the price of the phone up front, and about 200% of the price of the phone by the time they recommend you change hardware. Even a crappy phone is almost a thousand dollars now, and they can still be worth hundreds used after a few years, there are many places older used phones can be sent and sold.
Most of those types of plans have about a 50-75 dollar a month hardware charge built into the plan. A "bring your own device" plan is like 20-30 dollars a month. 50 dollars a month for 2 years is 1200 dollars. 75 dollars a month for 3 years is 2700 dollars. Pretty easy to fit the price of a phone in there somewhere.
Also their favorite customer, is the one that has a hardware fee in their plan, but then buys a new phone themselves from a third party. For people that plan to buy their own phone, make sure you are on a "bring your own device" plan. Save yourself hundreds of dollars a year. I know that part doesn't pertain to the person I am replying to, but I have talked to alot of people that brought their own device and were still on a 70-115$ monthly phone plan.
The phone company won't tell you about the other options, you have to ask, and some of the bigger companies don't even offer a plan without a built-in hardware surcharge. Then you better hope you have another option in your area. Most of the littler phone companies with dumb names aren't big enough to even offer hardware, so if you were ever curious why their plans can be 1/3rd the price, they are byod plans.