I think people who rally against Amazon in this topic assume that the "savings" from much open price competition immediately come back to the consumer or the manufacturer. In my experience, with previous such tech improvement such as 'uber disrupting taxies', this has never been the case.
Both the consumer and the manufacturer/labor/driver/gig-worker always get the short end of the stick.... once AI-agents becomes indispensable part of life.
I would be surprised if you had enough data to be able to conclude such a lofty claim, especially accounting for increased availability of taxis in areas where there were none or few.
Either way, the benefits of price transparency are not imaginary, but they are also not the only factor. Things like insufficient buyers or sellers, government policy, etc are also in play.
All else being equal, a buyer being able to easily see seller A is more expensive than seller B for the same goods will result in lower prices for the buyer. But all else is rarely equal.
Uber is a single centralized platform that sets prices based on their secret algorithm to maximize profit, gives worse deals to drivers who look desperate and shows different amounts to two riders standing next to each other. It's as far from real competition as you can get.
It would be way different if it was an open network where drivers are allowed to set prices and reject rides without any penalty, and riders can send multiple offers at a time then take the best one. That would be a real competitive market where everyone is free to choose what they buy and sell.
In that scenario Uber would be one of many apps you can use that index the network, whitelist trusted drivers and handle payments for a small fee. And if you want to make a new app or do the whole process manually there's nothing to stop you. That's what shopping on the open web is like.