not necessarily, thanks to the joys of commingled inventory! "GNC Storefront" goes in to the same bin as the rando person who put a label on some melamine powder, since it has the same UPC. In fact this also applies to Amazon stock as well - with the exception of Amazonbasics since they don't allow third-party sellers of their own products.

Correct me if I'm wrong but while there is a way for sellers to pay for non-commingled inventory... this is not signaled to consumers in any way either, this is a benefit to the seller to avoid increased returns, not to you as a customer. So you have no way of knowing where any particular "sold by amazon" or "fulfilled by amazon" item comes from. Probably by design... it would not surprise me if "no discussing commingling" was a rule too. It's in Amazon's interest to keep this opaque so that consumers treat them all as interchangeable commodities rather than favoring one storefront or another. Consumer loyalty would be detrimental to amazon's leverage over sellers.

everyone hates the non-prime items because they come slower and frequently incur large shipping costs... but those are the only items that are guaranteed to come from a trustworthy supply chain (if you trust the seller). Prices are actually often higher than a direct transaction with a vendor because they pay large fees to transact on amazon's platform too, and the shipping costs are often more sensible as well.

You really need to price it out because between prime costs, platform costs, shipping costs, etc, amazon is often not that much cheaper than directly transacting with a merchant, and then you would get a trustworthy supply chain by default.

The only thing keeping me on the platform is the unlimited 5% back from the amazon prime card (vs 3% for the card without prime), which can be worth it for certain big-ticket, difficult-to-counterfeit electronic items... and even then, I may end up significantly reducing my usage because Amazon has recently sent me a warning telling me to knock it off (a string of items damaged in shipment). Well, I'll have to make sure I don't order anything I might want to return, then... and I'm definitely going to re-evaluate in light of the price increase kicking in for my next renewal. The platform flat-out does not work if they start getting bitchy about returns given how awful it is in other considerations.

I have seen a lot of suspicious "manufacturer" storefronts.