My father is a cab driver and your Math is way off course. In order to break even, Cab drivers and most travel agencies offering cab services use a mix of fare systems. If you are hiring a cab for a day, the cab fares are mixture of 'time' and 'distance'. For example, there is a minimum half day charge for 4 hours or 40 kilometer, or multiples of that plus any additional billing for extra kilometers driven.
Tourist cabs are charged separately.
Autos are far far cheaper than any cab you can hire. But the margin of profit in Autos is way less, so the general quality suffers.
The reason your Meru's, Ola's or even Uber can offer cabs for so cheap is they raise enough money to operate on losses. Bankruptcy is pretty common in this business. Every time I talk to my father about a new cheap travel scheme, he only asks me to wait for their imminent demise.
We've been in this business for quite some while to understand how this stuff works. If you wish to understand how sustainable cab business work, have a talk with the office cab drivers. You will get a peek into the life of people who sleep for barely 5 hrs/day and drive 300Km/day to make a living on 12000 rupees a month. All while charging a good deal to travel agencies.
Autos are going to make a killing. If you are thinking you are going to invest your way in to this market, then you are going to be in for a surprise.
There is a saying in my native tongue(urdu): "If you wish to destroy a person's life, get him to start a travel business'.