Airport Express

If you don't want to spend too much time on bus, you can take airport express to any MTR station.

Take Wai Chai as an example. There are 2 ways from Airport station to Wan Chai Station:

1)  Take airport express to Hong Kong Station.
     Interchange to Island line at Central platform 3 (to Chai Wan)

The fare is $100. The travelling time is about 38 minutes.

2)  Take airport express to Tsing Yi Station.
     Interchange to Tung Chung Line at platform 4 (to Hong Kong)
     Take MTR to Hong Kong station.
     Interchange to Island line at Central platform 3 (to Chai Wan)

The fare is $60 + $13.8 = $73.8. The travelling time is about 49 minutes.

Both of the above fares are much cheaper than taxi fare (~$300). The travelling time is almost the same. (~40 minutes for taxi)