I would gladly tell the casino so that they can protect themselves for a reward.
In my experience, everyone would actually say this but only a few would actually report the issue especially when they have everything to gain from it. 
Unfortunately, I think that most of the users who use vulnerabilities for their own enrichment do this without giving a damn about conscience and morality. After all, they internally justify themselves, as it were, with the thesis that they deceive me wherever possible. So why should I be honest. Especially if I think that no one will catch me and punish me. There is and even thrives a huge number of hackers who even guess that they can be put in jail. But they still do their dirty work and run around the world and hide from justice.
Alas, there are few honest and absolutely moral people.
They are clearly lacking on this planet Earth.
It does really depends on the morals of the person how he will approach on this scenario.
And sometimes, even if you say it to yourself, you won't do it, but when the opportunity presents, you may change your mind.
So we can't really tell what's going on with the minds of people, when you are already in the situation.
But of course, as much as possible, much better if you will do the right thing, so your conscience is clear and you have no worries in your mind.