Still, I wonder if these (arguably illegal) practices are still worth it for merchants and companies, considering that there's no enforcement and the majority of consumers don't drastically change their shopping habits when being abused.
What likely happened was that somebody had an old and broken Rode mic and decided to scam Amazon. They purchased a new one, put the old one in the new packaging, and sent it in as a return with "ordered by mistake" or some other reason that doesn't indicate a broken or faulty item.
Amazon warehouse employees certainly don't (and never can) check out every return item for full functionality. My guess is that at the most, they make sure it's not just an empty box or a brick.
So, the only signal that Amazon has about whether to restock the item again is what the buyer stated for a return reason. If they tell the truth, they might get someone to take a closer look at the item and decide that it's not actually new. If they lie, they are both scamming Amazon and the next buyer.
Amazon _could_ treat _all_ returns as defective and destroy the returned items (historically how many brick-and-mortar retailers did it), but given their generous return policies, this probably means quite a big hit to their bottom line.
For example: only sell returns as "open box". For some items, I'd be happy to chance an open box, for other items, not so much.
Dealing with the cost of returns is a major part of a modern retailer, and Amazon has got to be through the roof with the numbers they receive.