If you can afford to risk a huge amount, you can also win a huge amount as well. That is how the high rollers mindset is. However, this is not about who can afford to spend huge or small amounts. If you are not lucky, you won't get any. Of course, they are rich, which makes them not worry about gambling such an amount.
Could we say these types of gamblers know the potential of gambling, or do they just rely on luck? Honestly, I don't think they will rely on luck but rather believe in having the chance.
Gamblers can win big by betting with small money but high mulitplier or they can win big in another way by using big fund for bets with low mulitplier for better chance of winning. The second bet style is safer and it is preferred by experienced gamblers with good capital as well. The principle is similar to anything you do, protecting your capital first before thinking of winning, profit, big win, whatever. If you take too high risk, life won't go like "high risk, high return" as in most of times, you will lose your money.
The second bet style is also good for risk management, and this way a gambler is gambling responsibly as well. It's good for that gambler in the long term of betting while it's good probability for avoiding losing initial capital. If he does not lose his initial money, there will be lucky bets to bring wins later.