Seems more mixed for me. Yes, Amazon is not guaranteed to be the cheapest so it pays to compare prices fro non-trivial items but often enough Amazon will still be the cheapest for me.
Also, grey market products aren't junk - they are by definition the official product just without the price gouging the manufacturer does in locales where they can get away with it.
Amazon used to have the best prices, but that is no longer the case. Just a couple of weeks ago, I needed to get bulk cat food (for a bulky cat). I tried Amazon, but they wanted double what I would pay at chewy. So I got it from chewy, and will never look at Amazon for that kind of thing again.
I also tend to go directly to manufacturer Web sites, and order from there. The price is seldom much higher than Amazon, and I won’t have to worry that I’m getting a fake, or gray market junk.