I'm not disagreeing here, but it could be that the fraud is a drop in the bucket of Amazon revenue. And just trying to get metrics on it, may cost more than what Amazon benefits from it.
I tonight bought a 3d printer hotend from the source company, because I couldn't be sure the product I order from Amazon would be genuine.
It's pretty bad when the products being sold on Amazon are labeled "Genuine assembled E3D V6 Hotend", when if Amazon gave a shit, it would only need to say "Assembled E3D V6 hotend."
Anedoctes are not data, but when you have some with no data, instead of ignoring it you should take it as a signal to go search if there is data to support it. Great scientists and mathematicians usually have good intuition of things to research, not because they have data, but their mental models of the subject tell them that there should be interesting data there.
You can think many things of Bezos, but he does know how to make a business make money. Data is important, but things that are hard to measure that you only learn as anectodes is also important.