the one that will extract the most profit from consumers' wallets
Oh, dear, an article by a Marxist still living in 1860. They love them class warfare vocabulary.
The online shopping sites are not trying to get the highest price they can for every product. They are trying to get the optimal price for every product.
Often times the optimal price can be the lowest price, or close to it. One only needs to look at Walmart's position at #1 on the Fortune 500 to understand this is true.
The optimal price is one that enables the highest overall profit for the company. Keeping customers coming back is absolutely one requirement for maximizing profit. Low prices directly benefit consumers and producers in many markets.
What Marxists fail to understand is that profit is the information signal that is sent through the economy from consumers to producers to indicate that they approve of what they are doing. A 'Like button' in the parlance of our times.
Profit is a very good thing, and it benefits consumers by constantly refining the goods available on the market and the prices of those goods.
Granted, Marx didn't have the benefit of game theory or information theory to work with, but modern writers have no excuse for ignoring modern learning (that's already 60-80 years old). Here's a recent Freakonomics episode on price elasticity that might help some aspiring writers (or even economists) who don't even want to take the time to read.