Good as you stated clearly in your last paragraph that human want are insatiable. its because of desire to make more money that attract men to gambling, some one that earns huge salary of $5000, would want to play gamble to double his source of income, while those that wish they could have a job that pay $100, are also using their money to gamble just to double what they have at hand. Human is naturally greedy, and also want to achieve more.
There is not amount that is enough to win a day, even if you win $1.m, it will not stop a gamble to stake more. The only limit we have in gambling is the stopping when you are losing much. You have to stop and take break, then continue again. But if you are winning it will be hard to stop because of our human nature.
To me, it actually does not depend on how much I win a day, but rather on how much I can be comfortable losing in the first place. The thing is if I can earn a respectable multiple of my stake, say 10x to 50x as you put it, that is a nice thing. But truthfully the human aspect drives you to pursue even more once you start winning and this is where discipline plays a central role. Losing is something that is easier to manage when you have a clear border and you do the latter. It is the reality of the case, that there is such feeling of the boundlessness in winning but there are lessons to be learned about when to quit and that is learnt through losses. It is less of managing money and more of managing yourself in gambling.