Basically, slot machines earn on average from $200 toR$300 per day, depending on how popular is that slot machine and what is the house edge. Since players don't have any way to impact the outcome of the game, slots make a guaranteed profit for the casino in the long term.
Yes, slot machines are profitable for casinos. Slot machines are designed to generate revenue for the casino over time. The odds are set in favor of the casino, ensuring that they make a profit from the money wagered on the machines.