TOI has this piece on Online Travel Agents in India.
The survey about locations of users is important. It shows the readiness towards e-commerce in India and where a location specific service (local search, order aggregation, ) might work. More on this later.
There is something even more interesting. The number of tickets that leading OTAs book per day. MakeMyTrip.com books 8000 tickets a day. ClearTrip.com books 6000 tickets a day. This number has been reported by the company themselves. There is no reason to doubt the accuracy. After all they are not like social networking websites where the number of members is the only way to evaluate these companies.
Going by these numbers, Cleartrip.com books approximately 22 lakh tickets per year. I assume this number to be correct (don't know if these many people fly in India per year) and going by earlier post on Cleartip.com earnings, average billing per ticket is 3200 bucks.
And again assuming that they get between 1% and 5% of the ticket as commission, they make anywhere between 50 and 250 bucks per ticket. This is a big range but without data, this is the best number.
Cleartrip.com earning report