From what I have heard and from research, most in flats get around a third to half of the price you give them.
For a girl from a flat, $2000HKD a day is more than reasonable, for a hotel girl, more like $3500 is generous.
I know one girl, she doesn't advertise, takes referrals only and clears 150k plus per month.

There are a few girls that do very well. While she is also more expensive, she is more than worth it. Ever session is total GFE, she is usually booked a week in advance, only a handful of bf's, as she calls them, a day... she takes her job very seriously, makes sure every guy is 100%plus satisfied. If you saw her on the street, you might glance at her, think she is cute, but that is about it. Worst of all, she is leaving HK for good in two weeks, to get married, and I can only get to see her once because I am going away on business.... damn!!
I mention this because sectorlord thought 120k was a lot, I know a few girls making far more than this, above is one girl. They aren't the high volume girls, most take just 2-4 a day, give each guy 1.5 to 2 hours, with time for recovery between and to clean flat, but these are the gems that are hard to find and more hard to keep.