why don't you just stay in a regular hotel?
I visited the Park Royal a few weeks ago, their 'serviced apartments' are just regular hotel rooms with a small kitchenette crammed in. they told me the rate was $24,000 a month, which comes out to be $800 a day.
The Horizon Suites in Ma On Shan is not too far away, but their monthly rate is somewhere in the same neighborhood ($18k-22k i think, depending on the room). Either way I don't think you'll get down to $550 a night.
Also Shatin is on the KCR, so you can stay in Kowloon and get there in a few minutes (E. TST station to Shatin is ~16 minutes only). So you can probably find something below 550 if you're willing to stay in Mongkok, Kowloon Tong or TST...
eg:
http://www.hoteltravel.com/hongkong/...ford_hotel.htm