This is probably similar to alcohol regulations. It's not illegal to sell booze to say, a 35 year old housewife in a lot of places. But when she's too drunk to remember her own name often now it's illegal to sell her more booze. Lots of people enjoy booze, what she's doing is no longer enjoying booze. She's got a problem and so we decide it's illegal to make that problem worse.
As with booze, for some people these things have no pull. I feel no desire to drink booze, and I also feel no desire to buy video game coins. But that's fine, the regulations aren't about me. Regulations protect the vulnerable.
It'd be cool if a nonprofit free to play alternative was set up to cut into some of the damage these do.
You can choose then, the simple option is our customers can't spend enough to go over that line, the potentially more lucrative but difficult option is check on your "whales" and only allow those who match affordability criteria.
I'm strongly against lootboxes and very concerned about videogames that are effectively casinos, but what the op described is just a videogame
I do understand the dopamine process of demo games on casino sites, but still. Allowing people to pay for that...