They're not perfect, and I think Amazon does combine listings for the same item (see "other sellers"), but the bigger issue is that the system prioritizes getting you exactly what you ask for over warning you of weird market shenanigans or out of stock sellers meaning prices are way higher than usual.
If Target is out of the brand of paper towels I like I don't go to the next store and buy them no matter the price, I get a different brand or skip it. If I had a human shop for me, they would also get a different brand of skip it. But that logic doesn't work with Amazon so it's not safe to trust it.
No, they aren't. GS1 - the organisation that administers retail barcodes - has rules about when to change the Global Trade Item Number for a product. The GTIN is what you probably mean by 'UPC' but GS1 now distinguishes between the abstract product number (the GTIN), and the concrete barcode symbology containing a 12-digit GTIN (UPC-A).
The Guiding Principles are:
* Is a consumer and/or trading partner expected to distinguish the changed or new product from previous/current products?
* Is there a regulatory/liability disclosure requirement to the consumer and/or trading partner?
* Is there a substantial impact to the supply chain (e.g., how the product is shipped, stored, received)?
Last time I looked at it, they fell prey to the region-locking-franchise nonsense. Something like each country had a registered office that would manage their namespace of codes with some sort of segregation or grouping.
Ofc what inevitably happened: same product from same company had two codes because because. Heinz Ketchup in Germany is not the same as Heinz Ketchup in Australia...and no one can tell you why.
Different recipe? Labeling? Different sizes... 160ml vs Country Z standard of 13.2oz, etc.
Oh and different codes for different groupings. Pack of 6 somethings got a new code VS the item itself as the barcode.
Not sure if you encountered the same shenanigans but I just stayed away. This is ultimately a people co-ordination problem and everyone thinks they're special. Meanwhile China spams all our market places with "Wish Wonder Elements Store" sellers that sell "40mm 1/2/6 pack of nail screws, woodworking, drill, conical shape, amazing product $1.22" and 5000 variations across all their sellers.
