I make a habit of asking support whether things I’m buying are commingled. First-level support used to be able to tell me pretty quickly (and I got both “yes” and “no” answers), but these days I’ve had to escalate most of the time. Kind of nuts to me that it’s worth ten minutes of support time and twenty minutes of supervisor time for them to sell me a $3 usb cable, but they’re the ones paying, so…

I would think that it would only take one or two incidents, to destroy that whole business model.

Vendors can be flexible, if the malfeasance is under the Amazon imprimatur, but it's a completely different story, if they act as fulfillment for a separate company, and substitute fake stuff.