> Is it really that hard to grasp that concept?
And then with more people with more money, businesses respond by raising prices until $15 no longer has the buying power it used to.
Why'd you stop your analysis half way?
Because these businesses have no competition that will underprice them by a bit and take all their customers?
You can tinker a little with the law of supply and demand, like this would, but you can't repeal it altogether.
To be fair, eventually that $15 won't have the same buying power, just as the $1.60 per hour 1968 Federal Minimum Wage no longer has the buying power it did back then (4 to 5 gallons of gas or packs of cigarettes, or 16 soft drinks or candy bars, or 10 comic books, or 2 paperback books, or a fast food meal for 2, or movie tickets for 2, etc.)
But that's eventually, not instantaneously, and in the meantime, it can do some good and stimulate local economies.