You need to look for (or limit your search to ) "Sold by Amazon". Not so say that Amazon doesn't sell some duff products, and they have some "private label" products of their own (Amazon Basics), but all of those will have had some degree of vetting.
https://9to5mac.com/2016/10/19/amazon-fake-apple-chargers-ca...
When I was looking at selling my creations on Amazon, they had an option to commingle stock with other sellers of the same item, but I don't know if that includes Amazon's own stock.
Link to my original post: https://news.ycombinator.com/item?id=12832605
Another trick for the best price is to not always go with the buy box by default. Amazon doesn't give up the buy box unless the competitor's price is significantly lower than theirs. It's always worth taking a look at what else is listed in the 'Other sellers' box, especially on products where Amazon is the vendor. It's likely their the cheapest, but that's not always the case.
I became a seller on Amazon two months ago, because I'm developing new (unique) products and I thought it would be simpler to have them distributed by Amazon.
But making said products is taking much longer than anticipated, so in the meantime, and as a learning process, I started selling one product in "private label" mode (ie, a product that I buy "as is" from a Chinese factory, with my brand printed on it). It's kind of selling, although the competition makes it hard/impossible to turn any profit (since all products are virtually identical, competition is on price and maybe listing quality/exhaustivity).
But what is amazing to me is that a service called "Amazon coach" regularly sends emails to encourage me to sell more PL products. Today, Amazon coach recommends selling a meat tenderizer on amazon.de: there are already over 350 different listings for meat tenderizers on amazon.de, how many more do they need???
Some time ago I used to regard the "ships from Amazon" or "Prime" logo as markers for quality, because I figured, somehow, that Amazon did some kind of vetting before accepting a product for shipping. That's completely wrong. The sign only means that the product is stored in their warehouse (and will therefore probably be delivered on time); but it has no meaning whatsoever regarding the quality of the product. There is zero curation.
Selling on Amazon is teaching me to trust Amazon less.
And of course, the ocean of similar products makes shopping much harder; meat tenderizers are not the worst case by far: if you're looking for a corkscrew in the Home & Kitchen category, you're looking at 2,500+ options on amazon.de alone... and 16,000+ on amazon.com!! Crazy.