You haven't actually rebutted the statement at all. Do you have any proof or rationale for this statement, or are you simply assuming that retailers don't do this?

And your example does not illustrate dynamic pricing at all. There's nothing dynamic about your example, this is all fixed prices quoted by merchants with different costs and profit margins. This is how trade has worked for approximately all of human history.

Dynamic pricing means that the price changes dynamically, in real time. Prices change based on time of day, weather, how many people are in line, what the merchant's algorithm thinks you personally are willing to pay. This is all new, enabled exclusively by modern computing and surveillance technology.

I don't think you actually understand what you're arguing against here.