In my opinion, GR is as much as profitable as other train in IR....some of my views are...
1. GR runs full in every trip becz of low 3Ac cost also it have extra seats (in many) that is side middle birth, 9 in number... So on an avg 9000 more earning for IR. (Patna-Delhi)
2. IR try to gain some more earing by tatkal schemes. Note: it have 200+ 3Ac Seats as tatkal that is also a factor. On every seats they earn more compare to express...
more... trains. If we combine SF total tatkal seats in SL And AC that would be less than GR tatkal seats(mostly)
3. Bedroll charges and catering facilities cost in GR. As it is fully AC so govt could give contact for catering facilities on more high price.