amazon sold me previously-owned earplugs
Amazon policy is that if a returned item can pass as 'new' it gets processed for resale as new even if it has been used, as opposed to processed as something that needs the price knocked down. Certain exceptions apply, if something is going to be unhygenic to process, or just might be unhygenic*, it just gets flagged for disposal.
Sometimes this just means replacing tape and other seals, if the original seals were generics then the item gets sold as new with replaced seals. Often this just means someone opened the box, decided the item wasn't the right size and sent it back. If the seals were branded then it gets sold as second hand, or is supposed to at least.
Sometimes it means the item gets cleaned and then resealed. Had a pot come through when I was working for Amazon that had traces of liquid residue on it, oil I think, got told to clean it with the supplies at my desk, replace seals and mark it as something that could be sold as new. Technically fine, but still something I felt was dishonest.
Thing is that some items get through returns with poor quality control. Happens when people are rushed or a given item's dirt or damage isn't immediately obvious. People like small items like earbuds, jewelry and so on because you can inspect it fast, and the size of items doesn't really matter for your quota, but it means a lot get minimal inspection so people can plump their numbers.
Worst thing for it is costumes. A lot of costumes get returned after holidays like Halloween, and it takes ages to check them for damage, and it's not like Amazon has an in-house laundry service to clean them in, so costumes in all kinds of states just get shrugged at and passed along to the auditors, who in turn usually just shrug and pass them without checking them. Looking for a penny sized stain or small tear on a lion onesie or whatever is a pain in the ass and slows people down, so it just gets kind of ignored.
Returned or undelivered food items just get marked for disposal, which I think usually amounts to being sent to landfill. Always found that apalling, as it didn't matter if the item was something with an expiry date measured in years, it all got binned.
*Like a sex toy for example, if it's been delivered and returned it gets binned. Doesn't matter if it actually got used before it was sent back, it's just that it might have been and therefore poses a potential health risk.
Earwax is generally not harmful mind you, it's a protective substance with mild anti-microbial properties. So long as the person the earwax is from didn't have an ear infection it's perfectly safe, if a bit gross.