this way u r cashback amount goes to pay tax like agent charge and payment gataway. I remember lst time i did some calculation and found out: Buy gift card and load amazon pay wallet then use IRCTC website and there u will get amazon pay wallet to pay (u can save agent charge rs40/- and payment gataway chare is 1.8% which is less compare to MMT gataway charge + amazon gift card 5% cashback using sbi cb)
MMT UI is convinent so even if u consider that then giving away of 5% cashback make sence