No offense but Apple is one of the only manufacturer which requires you going through them to get a battery change and aggressively restrict the availability of spare parts for their phone.

It’s also not cheap at all especially if you don’t pay their extortionate extended warranty fee which should be included from the start.

You don’t have to get the battery through Apple.

The spare parts are readily available through their parts portal.

And it cost less than $100 to get the battery replaced on any iPhone as far as I’m aware at an Apple Store without a warranty.