What is the cost and time of public buses, beside taxi, from Luo Hu to HK Airport? Thx

There is no direct bus that can take you to the airport. So you are suggested to take East Rail Line to Sha Tin Station, Exit A4. Then take bus no.E42 at Sha Tin Central Bus Terminus, and arrive at the airport directly. This bus line still operates at that time.
The whole way takes around 120 mins. It costs 43.3 HKD per person.