Casinos know this, and they take advantage of this knowledge. For example, blackjack is a game of skill, and the card counter has a higher probability of winning in 21 than when placing bets on slot machines.
The way casinos use these probabilities is expressed in playthrough contribution. This has something to do with the wagering requirement. Earlier, we discussed this requirement, and the one we used as an example was $500.
If you wagered $5, the same amount would be taken off the $500, whether you win or lose. Now, you only have to bet $495 to meet your target of $500. If you are a good player, and if you choose blackjack, chances are that you will meet that target easily. Just win 100 times, and you are good to go. Read more