Can I somehow check how much gambling sites make ? Daily , Weekly , Yearly , doesn't really matter but the more the merrier.
It's "impossible" for some sites but not for others....
For example... you can follow second trade ! (because they have only some address and you can see all txs for each address).
But meanwhile you can't see for Direct Bet... Every User could get a new address to send btc ( or other crypto) is quite impossible see all btc wagered and the profit of this site.
Following all transactions is going to be a tedious task.
Gambling sites are regulated and as far as I know register their business to every state and so they may have to pay to IRS which means there is transparency to their records.
No matter that your purpose of asking these info, but sure they earn big. Some of them support and donate charities.