nt.pilot
The flat in the link you gave is in Tung Chung, which is right next to the airport. The area is home to a lot of aircrew, with food and various amenities well within reach. It is about 30 minutes train ride to the city centre, pubs and nightlife though. Discovery Bay should be out of reach for a new S/O, unless you pitch in and share a place with several other people. This might be a good idea if you want to live in a bigger shoebox, but if you prefer to live alone, I can assure you that reasonably-priced rental accomodation is available in different parts of HKG.
You shouldn't need to fork out an unreasonable sum of money for food and utilities in HKG, so your biggest expenditure by far will be accomodation. Having said that, for the first few years you can expect to retain a bare minimum of your income. Things will gradually improve as you progress up the ladder into the F/O ranks, provided you stay single. Don't come to HKG expecting a lifestyle resembling the one back home, because you won't be able to afford it. Adjust, assimilate and you can definitely learn how to enjoy living in this city.