I would not pay 2500 or 1500 for the 10-15 min ride to the hotel.
As for the taxi service there are two types one of them is the Black and yellow taxis you get through the prepaid booth ( you pay the money upfront at the booth and get a copuon for your destination). Should cost about Rs,200 for the JW (approx US$4). These are bad cars which are non airconditioned etc.
Another option as you exit the arrivals area is the Mega Cabs (these are what you call radio cabs in India) they have an agent standing by who will put you in one of their cabs. (sort of decent cars bit small but airconditioned) and you pay based on the meter plus Rs.80 approx airport charge roughly to the JW about 300-350.
If you prefer something better still there are number of counters before exiting the terminal building offering car services such as carzonrent etc they will run you approx 700 to the JW you can also book these for the day or half a day etc.
All three options are safe, just avoid the touts or people offering services when you exit the building.