An example with base normal quota fare.
Train No: 12622
From NDLS to MAS
Class 1AC fare is 5125 X 18 berths = 92250
Class II AC fare is 2970 X 46 Berths = 136620...
more...

Class 3AC fare is 2020 X 64 Berths = 129280
SL fare is 780 X 72 Berths = 56160.
From this only we can understand that AC is more profitable than SL. And SL make more loss to railways by entertaining the waiting list people also.
Thats why IR is planing to increase the noo of AC coaches in most oof the trains.
Its a news that i heard and was not a confirmed, that There are plans from SR to increase 3A coaches in 12625/26 by reducing the SL coaches. The main challange for this is sghortage of AC coaches. But they will surely do this in future.