Ask HN: Utility Analysis of Owning a Smartphone

I went to my network provider's store today to upgrade from a Galaxy S3 to an S7 Edge because they were having a sale. I ultimately rejected upgrading because it would have bumped up my fees by $970 over 30 months. The marginal utility I would have gained from the upgrade did not seem worth the fee bump. What are your thoughts on the utility you get out of your phone plan, and do you know of any analyses that have been done exploring this topic?

Background: My S3, purchased three years ago, was a penny promotion purchase, but the store workers entered the information wrong into my plan, so I now have a 15% discount every single month, not just for the first couple, like the deal was supposed to be. This is one line in a family plan. The family plan as a whole costs way more than that. I understand that this is a special case because of the erroneous discount each month, but it opened my eyes to how much more some people must be paying for their plans, which made me want to find some sort of analysis about the utility people actually get out of their phones vs the price they pay for that service.

I think my plan now is to run my S3 dead then purchase an unlocked phone off eBay.