Some airlines like 6E and UK have a discounted rate for international travelers making domestic connections (they allow for 15kgs free luggage however vs. 25kgs for AI). I don't think AI has such discounts.

So depending on your total luggage weight and the cost of the tickets etc.. if might make more sense to either buy a through ticket to Surat, buy a J ticket with AI or buy a Y ticket and pay for luggage, buy a ticket with with a third airline and pay the international connection baggage fees (eg: https://www.goindigo.in/information/...l-baggage.html).

Since you've already bought your tickets, unfortunately you don't have much choice other than paying the absurd baggage fees. I think it will be higher than $137. On 25kgs, prepaying will help you save a few bucks.

https://www.airindia.in/Domestic-Wei...ge-Charges.htm otherwise Rs.600/kg at the airport. GST will be additional on both charges.