Simple Definition of extort. : to get (something, such as money) from a person by the use of force or threats.
No one is being forced to threatened.
I think it's a perfectly acceptable use of the word. The implied threat is that the customer won't get the product without paying over-inflated prices. Does it meet the legal/criminal level, probably not. Does anyone who's ever who's been the victim of such practices know exactly what I mean, yes.
It's too easy to just blame the people who are simply trying to buy something they value and desire. We all know it's just greed to jack up prices in the manner described, or at least we should know.
Anger where it's deserved, frustration where it's deserved.