> The number of humans available to perform daily investigations versus the total number of products sold makes this most decidedly not "easy".

Only if you're taking the blinkered tech mindset that employing people to do anything is hard. Amazon employs 1.2 million people [1], and has people employed that literally touch every single physical items it ships at least once. Every time you contact them you talk to one of their thousands of customer service agents. It's totally easy for an organization like that to staff a compliance department to investigate policy violation complaint.

[1] https://www.yahoo.com/now/amazon-projects-strong-holiday-sal...