To avoid such scams you should invest your money only in trusted sites and those details you can find it easily from this forum if you spend some time here. Also, you shouldn't put all your money in single site but try to invest in few good sites then you're chances of making a profit from these investments will increase.
If someone wish to see the comparison of how most gambling sites is doing here in general then take alook at dicesites.com. you could see the wagered amount as well as the profit made daily and compare it with some other sites as well , so anyone could do their own research regarding which is the best sites to put their money in
But its a widely known fact that " anything that sounds too good is probably scam" so if some sites shows huge profit not always means that we should blindly invest there.
There are difference between empty words and words with statistics. If we do our research, we can stumble on some investment sites that offers investment with high returns but does not provide us their statistics, e.g. a trading site that offers % increase and telling people that their gain is somewhere around 50% per day but does not show the proof of their threads. This is more likely a scam attempt to lure people and invest to them.
While some sites will show us statistics, example, a Casino Online sites, that show wagered bets and all the statistics of who wins, how much and vice versa. Then at the end calculating the net profit from those statistics. If we saw a big number of earning here, we can verify it by checking the stats presented. This is no empty words but actually a fact that whenever a person invest on that site will more likely earn certain higher percentage than other.
For a crowdfunded sites, you cant really fake any statistics. If you fake any of it then people will know it. For a crowdfunded site, every lost from gamblers goes directly to the investor therefore if you fake it then you will still need to put in your own bitcoin as the investors' profit , besides that gambling sites is known to make profit therefore seeing that most people got profit from gambling sites investment is just plain normal things