Yeah it's a slippery slope. Blizzard is particularly playing with fire when it comes to this.
At Blizzcon, kids can buy coin tokens with real money that are used in slot machines that give mostly random generic prizes, but the highly advertised posted allure was the very low chance of a very valuable prize, worth real money. Literally slot machines for kids, in real life. The only difference being you have to exchange money.
5-10 years from we'll likely be reading about lawsuits stemming from that.