The requirement is that the expected value for a play on a machine is >75%. And most are >90%. But that’s not a cap on profit margin, as 25% of the expense for a play may be more than the cost of that play.
Eg, having a machine that costs $1 with $0.75 expected return (and $0.25 revenue for the casino) may only cost the casino $0.10 a play — which would be a 60% profit margin.
Gaming does have expenses -- labor (mostly dealers and slot attendants & mechanics), costs of purchasing and leasing the machines, and some other miscellaneous stuff... but profit margins on pure gaming are very high (and not limited in any way by the 25% maximum hold percentage that you reference)
Now the casino has your dollar and it's "costs" were four cents in electricity/maintenance. A much higher profit tham 25%.
Other businesses are treated like this too. If you are a high frequency trading firm and you buy 1000 shares stock for $99.99 each and sell for $100, you didn't have $100k of revenue - you had $10, and your profit is what's left after paying for staff and computers.
Yes, if your business was a supermarket, it would indeed work the other way, and it's not obvious to the literal- minded where one treatment should stop and the other should start.
And perhaps is more obvious when you consider what happens when there’s only players, eg, poker. The pot is held in trust, until the game ends and the losers forfeit their money to the winner. At no point does it belong to the casino.
That doesn’t change when the casino is also a player.
So no, profit is more like gross revenue minus expenses and taxes.
You could easily have a machine with positive EV for the house that has negative profit.