The labor cost for replacing parts on a car isn't just another ballpark. It's another planet.
Obviously if you want to replace every part of the phone it is going to cost more altogether than a new phone. No reasonable person would argue that. And of course there are limits. The screen and mainboard are by far the most complex parts. The frame is trivial by comparison.
The problem is that there is effectively no real aftermarket for parts and repairs. Apple all but refuses to sell parts and makes using third party parts as onerous as possible.
They have been able to get away with it so far by riding the wave of quickly advancing mobile technology. But as next year's phone starts to look less and less different from last years phone, people are going to start to get serious about repairability and Apple is going to be forced to make some changes.