I think the cheapest and moat convenient way is to commute in shared taxis. Ylu have innova, tavera and scorpios. You can board thrm at gumat. There's a taxi stand there. You can easily bargain on the price quoted by them. And also you can sit at thr back sit of that taxi. The charges for the back seat is lesser compared to front and back one.
Hello Riya! Road journey from Jammu to Srinagar takes around 7-8 hours. If you want to travel in budget, bus is the best means of transport to commute between two cities or you can go in a private taxi. You can easily find taxis at Jammu Railway Station. Also, you can take a flight from Jammu to Srinagar airport that's the fastest means but not as cheaper as a bus ticket.
Well If You Keep A Closer Look At The Airfares I Am Sure You Will Find An Airfare At Par With Surface Transport Only If You Keep Track Of That And This Route Has A Tendency Of Unexpected Fares!