How much does a battery replacement for iPhone 11 Pro Max will cost?

Hello Izngwenalthea!

Yes, that battery definitely needs to be replaced!

According to the “Get an Estimate” tool in here, the battery replacement will cost $90 United States Dollars (USD).

Have a nice day, and good luck!

I have an iPhone 12 How much does it cost to replace my battery

Same price as mentioned above. $89 (US) at your Apple Store Genius Bar.

You can use this to make an appointment --> iPhone Battery Service - Apple Support