I often think about how there's an open question in this case of whether it's necessarily anti-social for a market participant to fight hard to create the level of critical mass necessary to give most people the product they want.

Everyone likes stuff showing up at their door reliably wherever they are, and this isn't possible unless you have a service with warehouses and dense customers ~everywhere, and this isn't possible unless enough people use that same service. So in one sense it's in everyone's interest to have an assurance contract where everyone says "I will use this service if you do." Then in that sense Amazon's price rule is building a mechanism to support such an assurance contract: you can't force people to sign such a contract, but you can prevent people from defecting to slightly lower prices outside of the "stuff just arrives fast" system.

In a system that was very good at collective action outside of markets, a cleaner solution in terms of consent and power might be to build an actual explicit assurance contract for an app-to-door-everything-delivered-fast service, get everyone to sign it, and make a public utility and/or separate dis-aggregated markets for the different levels of service provision, whatever they are (consumer facing app, supply, warehouse, delivery, etc.). But anyone who has ever even thought about doing anything like this will know that it's much easier said than done, and will appreciate the kludge Amazon and their investors pulled off, at least a little bit, the next time they buy a thing online.

Maybe the answer is just: use Amazon until technology (robotics e.g.) makes it easy to create something better? At this rate, we shouldn't have to wait too long?

It is surprising how often they are cheaper. I was ordering some glue, decided to double check the price, I could drive for 30 minutes and buy local, and pay more or order it for cheaper from Amazon. I didn't need it the same day so getting it tomorrow didn't matter. Amazon also sells everything need some M2 screws Amazon will have them, no idea where to buy something like that locally Home Depot won't carry them.

... and a lot of times I go right to the brand to buy "straight" from them and they fulfill orders from Amazon so why not just buy from AMZN where I already have an account, get lots of credit card points, can spend my credit card points, etc.

In the last year I've seen this other kind of consolidation where most of the brands that don't have an AMZN-hosted or fulfilled store are using shop.app (now shop.com!) from Shopify. I did a stint of investigating boutique perfumes [1] and it seems almost everyone in that business uses Shopify.

[1] you gotta try "Under the Lemon Trees"!

It's not price fixing. The seller is still completely in control of the price, but they cannot discriminate against Amazon by selling it cheaper elsewhere. Or they can, but then Amazon don't want to do any business with them.

These kind of contracts are standard for all kinds of third party marketplaces. You don't have to sell through them if you don't agree with the contract.