"Prime Sellers" (that's FBA sellers in Amazon logo) are not more trustworthy than merchant fulfilled sellers by any means. It's simply just a different way to fulfill orders.

Also its possible to get a knockoff product that is sold and shipped by Amazon because Amazon allows their inventory from their supply chains to commingle with third party seller inventory.

I too used to try to use that metric, but as you say, it frequently doesn't work. A highly tuned BS detector is your best tool ... and for better or worse, that's more and more true as time goes by in most venues.

Assume everything might be junk. Even some items from the best companies, i.e. I've been buying and will be buying more precision tools from Starrett lately, Made in the USA and all that jazz, and it shows. But when I went to buy a small metric open wrench set, the reviews indicated their's was anomalously subpar (so I went with another vendor with a good product, and then I got straight from Amazon Prime a mispacked Imperial set in a metric labeled baggie :-( Sometimes you can't win, although the return was painless (well, after I convert the image to a raster one, the normal shipping labels are the only thing that kills my heavy duty but old Brother printer, but not my father's much newer and cheaper one) since there's a UPS drop-off in walking distance.)

So, distrust and verify, and learn the particular patterns that signal relative trustworthiness, like 96% or better reputation for merchants (but if they don't do much business and are one of the few or only who sell the item, check the bad reviews because so many are self-evidently bogus), and of course shill reviews. And especially a fine tuned sense of "if it's too good to be true...."

Or take another example: pretty much all US market washing machines are shit, because the government pays the companies to make them worse and worse each year by using less energy (lower water temps, and I'll bet less agitation), Whirlpool, which only does appliances, paid no Federal corporate income taxes for at least 2 years because of this scam.

So when my 2007 not so bad GE washer had a $$$ expensive problem to fix (since to make it cheaper to manufacture, and a one level more reliable in the field, with a solenoid attached to a major part that you can't fix in the field without replacing everything), I checked out the competition, and Speed Queen's consumer line was highly spoken of.

Seems they bought an old Whirlpool? plant and rights to make an old model, which reading between the lines uses the old electro-mechanical cycle selectors/timers, which of course fail with some regularity.

But Amazon reviews saved me from a fatal flaw in their business model: if you need a major repair, e.g., due to a manufacturing defect (fairly rare) or shipping damage (it happens on big heavy items like this), you're SOL. They pay their network of third party repairmen a fixed rate by the incident, so if one of timers needs replacement they'll do it quickly and with a smile, if it's something serious they won't give you the time of day (so I spent maybe 1/3 of the cost of new Speed Queen on a repair by the local GE shop which my family has a 3 generation relationship with (my paternal grandparents actually sold them their first store front on Main Street, where they were selling newly hatched chickens and turkey, and it helped that the washing machine is of very good design and good build quality).

Which I can't blame them on, you don't make ends meet by working long hours at a loss, but let's just say that reviews like that make me a loyal Amazon customer, they've saved me enough money that I'm willing to pay them small premiums for the stuff I do buy from them, especially given how reliable that process is.