Is what every third party ever said. I wouldn’t be surprised even if you could claim to build an iPhone from scratch.

OP mentioned current iPhone has same resale value of original battery replacement from Apple. The wisest option is to upgrade with a trade in if he wants to use the phone trouble free in the long run. Otherwise, options such as third party battery replacements will only save you so much in the short run, let alone compromising on the water resistance. Overall, it’s a liability to use the phone from an iPhone for third party service centres handling the peripherals of Apple. I’ve seen centres where they charge customers through their nose and still don’t guarantee proper functionality. Customers upgrade their phones either way. Third party centres only profit for themselves.

Looks like you never owned an Apple device. Every Apple part has a specific code which is only compatible with that particular device. My cousin had almost everything replaced including the camera from a third party and nothing worked, mind you it was a 6S. The camera and microphone failed, battery never charged properly and the whole phone was a total waste. Long story short, get it serviced by Apple or trade in for a newer device with an accidental damage warranty using Apple care plus.

Not recommended to replace via third party. Either get it to Apple Store for battery replacement or trade in for a newer model.