Why do fares differ between travel classes?

Fares differ between travel classes because each class offers a different level of comfort, space, and services. Sleeper class has open windows, no air conditioning, and three-tier berths making it the most affordable option. AC 3 Tier provides air conditioning, curtains, and bedding with three-tier berths at a higher price. AC 2 Tier has two-tier berths, more privacy, and wider seats. AC First Class offers private cabins or coupes with the most space and premium service. The fare difference reflects the cost of maintaining air conditioning, providing linen and meals, and the number of passengers accommodated per coach.