The actual cost breakdown for a battery replacement is:
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
https://www.ifixit.com/Guide/iPhone+11+Battery+Replacement/1...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.