err...I dont't know of any AHK Captains who earn that a month I think your information is inaccurate.
From my very limited knowledge on AHK the command salary is 60k+ a year plus an hourly rate of over $40 per hour + other allowances. I would estimate that at around 7k-8.5k a month at a rough calculation on a average month.
How did they get to the 4000 per month figure - someone is telling porkies
An FO gets around 4k-5k a month at AHK.
Although I could be wrong but I dont think so.