Any firm with an Ingram account can pick up Ingram’s feed, and list books for sale. And, Amazon allows third party resellers to list these on it site.
It’s doubtful these outfits have your book in stock at all. Only if someone orders a copy from them will they then order a copy from Ingram.
Some of Amazon’s resellers also have numerous pricing errors in their databases. Amazon has thousands of resellers and contacting each one about pricing errors would be virtually impossible. If they have a book priced too low, they’ll learn the hard way when/if they sell a copy, and end up losing money on the transaction. If they have a book priced too high, the book buyer will simply buy the book from someone else. And, since Amazon’s database lists those reseller offerings in order of price, the buyer won’t have any trouble choosing the least expensive one on the list. These reseller listings are database drive so, in some (if not most) cases, a human being hasn’t looked at them before they were posted. If you do request a reseller fix an error, they may fix it, or they may simply ignore you.
If they do sell a new copy of your book at lower or higher price, this will not affect your royalties. You will still earn a flat percentage of the list price you chose for your book. If they do truly have a used copy of your book, you will not earn any royalties because you earned those when the original copy was printed and sold.