I don't think the argument is to reverse the original statement (the original statement being something like "the top spenders must be wealthy", the reversal being something like "the top spenders must be poor"). Rather, the argument is that knowing there are people spending a lot of money tells you nothing about the income level of those people. They might be someone who's independently wealthy and using money they won't miss, or might be someone who's quite poor who's damaging their life in other ways to obtain the money. The argument is you don't know which from the facts given. All you know is there are people who spend $X on it.

That said, I don't think income level has anything to do with it. There are poorer people who shouldn't waste money to play the lottery or gamble in casinos, but do it anyway. There are also wealthier people who shouldn't waste money to play the markets, or other "casino/lottery for rich people" things, but do it anyway. It's just that our society is mostly oriented to treat the poorer people as compulsive gamblers -- which is treated as a moral failing -- and the wealthier people as "serial investors" or other terms which carry a more positive connotation.

Being poor surpresses rational thinking, making them more vulnerable

https://www.theatlantic.com/business/archive/2013/11/your-br...

Perhaps people with addictive tendencies are less likely to become, and stay rich.