This already exists, albeit not in federated form. It fundamentally doesn’t work because the market players have an incentive to withhold as much information as possible, because any mistakes consumers make from not comparing prices is direct profit surplus.

Collecting the information in the first place is also difficult, because it would essentially require getting the consent of most sellers (which they are disincentivised to provide), or just scraping it (often illegally).

Thus, such an aggregator requires too much work/risk, which needs to be compensated for. Consumers generally don’t like the idea of simply paying for independent advice/brokers, so we are stuck paying in other ways, such as via personal data and behavioural surplus for commercial tech sites, of which numerous exist.

Most search engines such as Google (eww I know) already have a shopping specific search page. eBay and Gumtree also have existed for decades.

eCommerce platforms like AliExpress and Amazon also already do this, if you set the filters to only be third party sellers.

There’s also category specific aggregators such as PCPartPicker/Newegg.

We don’t even have a way to quickly search the freely posted text on the fedi.

The innovation for Amazon isn’t the product list, it’s the logistics. Without centralized warehousing and distribution you’ve just recreated eBay or Etsy.

Not a bad idea for small businesses - having a central place to purchase direct from retailers is a nice idea, I think where it may struggle is:

Verifying seller authenticity / avoiding scam products

• In a fully open marketplace its hard to enforce accountability. Amazon has teams of people removing fraud items (and they still have rampant fraud).
• Amazon functions as an insurer on sales - if you receive a fraudulent item, amazon eats the cost (and tries to cover it from the seller)

Part of Amazon’s market dominance and convenience is owning the logistics

• Amazon operates massive warehouses and has tons of money invested in logistics, so orders can be consolidated
• All of the savings of not paying the “Amazon tax” will just become the FedEx/UPS tax

This is not to say it can’t be done but Amazon has billions of dollars of infrastructure that’s hard to replace with volunteer programming

So 10 have the same product, then what? Race to the bottom again? What about key details that are not easy to see but can be important? Amazon really is shit in this regard already, but randomly mixing shops will only be worse.

I was thinking of this myself, but I think there are a couple challanges.

To gain widespread adoption, you need trust. This is complicated when you have a large amount of vendors. How are people going to access it? Will they go through different sites? How are you going to handle payments? And what if you buy multiple products from different vendors at once? How do you deal with a vendor misbehaving? Do you deferate with them, what if others don’t? What if a vendor spams or uses fall advertising?

I don’t think a federated webshop with the current fediverse model works, but I think it’s still possible with more organization.

There could be non-profit’s or coop’s that manages the single customer facing website, moderates the site, and other matters that need to be handled centrally. Similar to how there are people organizing real life markets that bring the stalls, advertise the event locally, etc.

The software behind the web store would be an open source project which receives funding through the aforementioned organizations.