I also saw a documentary on social media about a professional gambler who is a sports bettor in Las Vegas. He shows his mansions, expensive cars, and a lot of dollars in his house. He claimed that it is simple to make money from gambling, particularly in Las Vegas. He started with $50,000 and worked his way up to $300,000 in just three days! I am amazed. He really has not disclosed on what sports he is betting, but he just said that in sports betting, you will win big if you bet big, but the risk is that you will lose it all if you lose.
To be fair, $50k seemed something affordable in the eyes of a professional gambler, not to mention that this was probably one of the instances where he was pretty lucky. I'm not saying he doesn't win, just that it wouldn't be this much just in the span of 3 days for the most part. Selective advertising if that's a term?
Usually everyone agrees that in gambling everything depends on luck (and not on your mood or skills), and the advantage is on the side of the casino. Thus, in the "normal/average" variant, the player gradually loses money and does not consistently earn it (which is generally a rarer case than even the jackpot). Thus, it is quite expected to be surprised that someone plans to spend (and seems to really spend) the money that he earns on gambling.
I reckon in most cases of planning in advance in winnings, it's only a part of the profit that's realized. Like 1/4 of the entire bankroll would be considered and then calculate depending on the games they play. It might also even be an average in terms of their monthly winnings, which is probably not reliable, but hey, it's a reasonable measure.