Assad, it's up to you regarding accommodation.
The airport hotels (Regal/Marriott/Novotel) etc. are pricey because they are convenient. It's the same at most cities around the world.
I actually stayed on HK Island - there is more choice and the rates can be cheaper. I just picked one close to an MTR station, and from there took the Airport Express. I left plenty of time and it turned out I was first to arrive.
I guess it's a good way of getting acquainted with HK's public transport system. You never know, you might need to get used to it ...
