"with parity in delivery time, product quality, returns experience, etc."

How would the user know that? Many sites, including Amazon, make their bones providing decent quality at a lower cost, and then once they build up their market they start reducing the features and raising the costs. Amazon tends to be more expensive nowadays and suffers from product quality issues. It is super easy to use and has a good return experience, but it used to be a leader in all four areas.

And the AI replacement will be incentivized to do the same thing. And so will the LLM provider, etc. All businesses do this - once they acquire a dominant position, they start screwing over the customer.

Still can’t beat the delivery time though. Their logistics network is insane.