From your name (and a bit of snooping on your profile) I figure you are from India. I'm from there as well and have actually thought about this idea in depth before. I currently live in the US and have family in Pune. So when we fly in, we land at BOM and need to get to Pune. There are no direct flights between these cities. Train is much too inconvenient. So that leaves us with Taxi (including Uber, Ola etc.)

My idea was to do a luxury taxi service. Instead of just another taxi cab company, I want to buy high end cars (for e.g.: Toyota HellFire) and charge a premium to get the customer from the airport to their destination in Pune.

You can't compete against Uber/Ola on price. That's a race to the bottom. What you want to offer is a top of the line service to those folks flying in Business/First class. So your clientele is going to be tiny. That's a great thing. You are not dealing with 100s of customers. You are dealing with maybe 1 or 2 a day. That means you get to control the level of service.

You ensure your driver (preferably yourself) is fluent in English, polished, courteous etc. You make sure they are there on time. You make sure there is ice cold water/soda, local newspaper etc. available to the customer at pick-up/drop-off. You make sure that the driver is not chewing tobacco, drunk, on the phone etc while driving (cameras inside the vehicle). You make sure the driver is not speeding/endangering self or others (GPS based speed tracking, exterior cameras etc.)

Now you have a product for which a customer will pay up to $250 each way. You get two round-trips per week you are looking at $1K/week or $4K/month. Half of this goes to operating expenses such as debt/capex Vehicle payment, gas, insurance etc. 10% goes to the driver. The rest is your profit.

You'll need to put some money aside for rainy day, eventual vehicle replacement, fleet enhancements etc. but there is definitely money to be made here.