None of those are monopolies, unless you consider someone selling a sandwich on a particular plane as a monopoly and the people on the plane are your market, in which case it is exactly this situation, and why that sandwich doesn't cost $100.
So instead of trying to think of complications, you need to first understand the argument, and then you can see it everywhere once you understand it.
I’m simply saying it’s incorrect to assume that everything everywhere is as cheap as possible. This is true in MANY INDUSTRIES, but not everywhere, and it’s absolutely nothing like a rule.
You, I think, are tying it into a larger discussion about monopolies, but I’m not sure that makes sense because if you’re a monopoly, you don’t have competitors to beat on price, so you again would not charge the least amount possible. That makes no sense.