(Thought Apple's $99 to do the repair themselves isn't terribly bad all things considered; and likely part of their attempt to forestall complaints and litigations).
Part of the new requirement should be they can't kill battery lifespan in 2-year old phones through software updates, either.
Because even "replaceable battery" doesn't fix that serious problem!
45 EUR for a new battery
10 EUR for new display adhesive
20 EUR for screwdrivers and a spudger (unless you have them already)
a suction cup and tweezers you probably have at home already
Ignore the 25 EUR clamp and 20 EUR heat pack, I did and they weren't needed at all. So all in all, around 910 USD less than you claimed.
The heat gun discussion in the sibling comments is also completely ridiculous. There must be 100 ways to do it without a heat gun. Put it on the radiator, use a heat pack for muscle soreness, or just borrow a hairdryer.
If somebody's unable to replace their iphone battery because they can't come up with a source of heat, I doubt they'd even be able to replace the batteries in their TV remote.
Myself, I've had bad luck with getting things sealed up just-so in my own phone-repair adventures (which can be validated well-enough in Samsung world by looking at the barometer's reading, squeezing the phone to create some internal pressure, and then watching the rate of change).
I like to think that I have reasonably-decent mechanical inclination, but the luck here has been bad anyway. I really just want to be able to take the battery out, put a new one in, and have it otherwise work exactly like it did an hour ago. Alas.