"five..." - You wager $5. It is gone. It is the price of playing the game.
"...will get you $10" - $10 comes your way if you win.
There is nothing here about $15.00.
"I won $5.00 in the lottery!!" No, you didn't. You paid $2.00 for that ticket. You "won" only $3.00.
"I won $112.75 from the slot machine!" No, you didn't. You pumped in $140.25 worth of quarters and dollars. You actually "won" a NEGATIVE $27.50. We like to call this a "loss".
There is no "keeping" of your wager. Your up-front expense is part of the deal. If you get to take back your wager, then you didn't play the game and you don't "win" anything. Gambling is subversive. It wins. You don't. I once went through Las Vegas. I was young. I wanted know what this gambling thing was all about. I asked an employee, "Where's a good machine?" She laughed, "There are no good machines! Why do you think we keep adding on?" I pumped in my 75¢ budget, thought, "That was stupid," and went on with my life. Of course, if that's really how you want to spend your entertainment budget, that's up to you. This isn't really a morality speech. It's a hint that if you think gambling has ANYTHING to do with being FAIR, then you have not thought about it correctly. The odds are ALWAYS in favor of the "House". Always. There may be an up-front fire sale to make you start thinking you can win. Don't believe it. Funny thing is, those who do defeat the house once in a while are usually cheaters and they are thrown out immediately. But, I speak of institutional gambling. Your little $5.00 wager is based on an opinion, not an actual calculation of odds. Still, you don't EVER get to keep your wager.