The high-demand girls, those where punters are waiting outside, are probably servicing 8-10 guys a day.
But the typical girl probably gets 3-4. Let's say it's only 3.
$400 per session (includes tips) x 3 per day x 22 days per month =
$26,400 per month
Rent = $8,000
Utilities = $1,000
Laundry/condoms/etc = $500
Total expense = $9,500
TOTAL PROFIT = $16,900 per month
As a guideline, a typical University of Hong Kong (HKU) graduate earns $18,000 per month in his/her first job (
source). HKU is the best university in Hong Kong where less than 5% of secondary students will get accepted.
So a working girl is earning about the same as the brightest university graduates in Hong Kong. That's not bad considering she didn't have to spend four years at a university and paying exorbitant tuition. Not to mention, the working girl probably works fewer hours per week.