Once upon a time if I wanted to buy something, I would stick its name in Google and click the Shopping tab to find the cheapest. Often a random online retailer. Products and prices were scraped from the internet like any other organic SERP.
Then they started charging for access. The number of suppliers decimated. It was no longer competitive.
That allowed Amazon and eBay to become the bazaars they now are, including what TFA is talking about.