The issue isn't whether the marginal cost of replacing it is reasonable, the issue is why does it need tools and skills that people don't already have.
> the issue is why does it need tools and skills that people don't already have
Because these are extremely lightweight, compact, water-resistant devices. There isn't room for old-style battery compartments. Every micrometer is squeezed here.
Why? What evidence do you have that tools and skills are more important than marginal cost? It is less convenient, I agree with that, but the bulk of users live close to an Apple store. The other approach is overnight shipping service that Apple makes really easy to do. Call an 800 number, get an overnight box from Apple, send it off.
The other benefit is that Apple will make sure they all get recycled. I don't know this as a fact, but it seems that most of the folks who want to jump on this as evidence that Apple is evil are the same people who are willing to spend a bit more for greener solutions in general. Having Apple replace and recycle is greener than having millions of users tossing old batteries into trash cans. (Don't kid yourself, this will happen if iPhone batteries are easily replaceable.) Yes, there is some marginal cost for this ecological advantage. But it seems like a good tradeoff to me at least.
My 6s is 5 years old. Had the battery replaced once so far. Going strong running the latest OS. $49 for 5 years of use. Not too bad.
All in all, I just have a hard time understanding all the emotional anger over this issue. It is just not a big deal in practice (in my experience). I guess it has been a problem for others, although I wonder if the angry folks actually have iPhones. To each their own.
Doing it myself would require $34 in parts plus tools and skill I don’t have.
https://www.ifixit.com/Guide/iPhone+SE+Battery+Replacement/6...