I used some sites to earn satoshi like freebitco.in it seems like very legit and also its referral system works fine . I barely see advertisement in this sites But these sites already given huge payout How these sites make revenue apart from advertisement
It's on their website in the savings FAQs:
How do you make money to pay us interest?
When you hold money in your FreeBitco.in account, we split it into 3 parts - the first part is used to cover user withdrawals, the second part is used to bankroll our MULTIPLY BTC game and the third part is used to expand our bitcoin mining operation (which is currently 8.880 Petahashes or 0.238% of the total hashpower of the bitcoin network). We make a profit and assume the full risks of our businesses and in return for you saving your money with us, we give you a risk-free fixed rate of return.
Most people probably lose money gambling on the Multiply game, which is income for the faucet. And if you can afford to run a mining operation to begin with and know how to run it well, it can result in a decent income.