Is that an agency that takes a big cut of the pie and only pays their maid employees maybe 60% after taking their cut of the fees charged?
The Base has a huge amount of cleaners working there every day, as they have to prepare it for the next illegal short-term AirBNB renters coming to stay for a few days, which would include a full deep clean and change of bedsheets, towels, toilet paper, etc. 500 baht would make sense for something like that if all that was included, and that's probably the price the AirBNB'ers gets charged as a cleaning fee after they've trashed the place.