Successful games subsidize everyone else, which is not comparable to Steam or anything else.
Collectible items are fine and can't be exchanged for USD, Roblox can't arbitrate developer disputes, "black markets" are an extremely tiny niche. A lot of misinformation.
It's annoying to see these videos brought up every single time Roblox is mentioned anywhere for these reasons. Part of the blame lies with Roblox for one of the worst PR responses I have seen in tech, I suppose.
You have successfully made the case for a 45% fee and being considered approximately normal, or a 60% fee and being considered pretty high still. 75+% is crazy.
It helps that seriously marketing a Roblox game costs < $1k USD always, usually < $200 USD. It's not easy to generate a loss, even when including production costs. That's the tradeoff.
[1] https://youtu.be/_gXlauRB1EQ
[2] https://youtu.be/vTMF6xEiAaY