I don't know about Varanasi but the roundtrip economy airfare for
Colombo-Delhi is about 45000 rupees. Pretty expensive as even
Colombo-Changi is 35000. But the service is excellent and far better
than Air India. Sri Lankan is the best airline in central/south asia.
You can either buy the ticket from a Sri Lankan Airlines ticketing
office near you, any travel agent or from
www.srilankan.aero. If you
buy through the internet you will get a 5% discount.
2 domestic airlines in Sri Lanka are planning to start no frills
flights to several cities in India in a few months. They are bound to
be less expensive/
It'd be cheaper if you fly to madras (18000) and get a local flight
from there. Or you can just swim thru the palk straits lol. Watch out
for sharks.