Apple repair prices prices for Touch ID phones (6s,7,8,Se and their plus models) is ₹3500. Was told this when I got my 6s battery replaced (about a year back)
Faceid phones (X and after) were ₹5500 if I remember correctly.
sadly apple pairs and codes their batteries to the phone. With 3rd party batteries(even if they are authentic) you’ll have a battery warning message in settings.