In essence, players are buying chances to win when they put money into a slot machine. A percentage of their wager goes toward the casino's total earnisattaking upngs each time they spin the reels. Because not every player will get their money back; in fact, the house edge will cause the majority of players to lose over time, this model is sustainable. Although the house edge varies from slot machine to slot machine, it usually falls between 2 and 15 percent.