There are two flights from Beijing to Lhasa with full price ticket of 3,300 yuan per flight. A round-trip ticket from Beijing to Lhasa costs 6,600 yuan.
To save money, you can consider taking the flight from Beijing to Xi’ning and then take the night train from Xi’ning to Lhasa. A direct flight from Beijing to Lhasa takes about 4 hours and 30 minutes, a direct flight from Beijing to Xi’ning takes about 2 hours and 35 minutes, and a train from Xi’ning to Lhasa takes about 21 hours and 30 minutes.