For electronics products, some reviews go into excruciating details on what counterfeit v real products look like.
Then some products literally explain how to avoid counterfeit products, especially the smaller producers of goods with niche products.
Finally there are articles in the press about it.
eBay has less of this problem because it's set up to select sellers based on reviews. Amazon's stores are more obscure, and often don't have many reviews, or sometimes you get an item fulfilled from a third party without knowing about it. I'm not sure if that still happens though.
Amazon removed it years ago because they do not want to be in the law margin retail business. They want to only be in the higher margin platform business. And that makes me not want to support Amazon.
Yeah easy to refund but I spent 2 hrs insect treating my house now I have to do it again, not a pleasant task. Oh yeah now I have a roach infestation because the traps were fake. The effects are much farther reaching than you make it out to be.
I've bought 1,000+ items from Amazon over the past 10 years and exactly one item was counterfeit -- a camera battery from a third-party seller.
Honestly, worrying about counterfeits on Amazon, for items sold either by Amazon.com or reputable storefronts like Pharmapacks, just seems silly, it's so incredibly rare and easy to get fixed immediately with a single quick phone call to Amazon. And for third-party storefronts you've never heard of, it's no different than doing the same on Walmart.com or eBay.