One estimation that you can make is to multiply the house edge, which is usually 0,5% by the total bet amount.
This will be the betting site turnover. After that it depends on the number of employees, hosting, promotions, referral payments, etc.
That's a good method to estimate how much a gambling sites makes. Thanks!
Of course you can't say the precise amount but you will defiinitely pretty much have an idea.
Another way to know the amount is (if a site is based on investments) reading a quarterly statement for shareholders.