Present SL fare from Mumbai to Delhi on WR route is 615/- (Swaraj express).
If we consider it was 375 in 2003 then it's just 1.64x increase compare to rise 7x rise in per capita income.
And 3AC fare in same train on the route is 1610/- so a pax traveling in 2003 in SL class in now travels in 3AC would have to shelve out 4.29x more which is still lower then the rise in average per capita income over the same period.