For the most part, eBay can't "do something about this" because there's no actual law or eBay regulation being broken. It's not against the law to ask moon money for common, worthless coins. As Dilbert's Boss once said, "There's no law against optimism".
You know that coin is common and cheap, and I know that coin is common and cheap, but how is a non-coin-collector supposed to understand it? The "value of a coin" isn't a fixed, scientifically provable property like its composition or temperature. They can't apply fixed, scientific, provable-in-a-court-of-law rules to it because the coin market is essentially emotion-powered, where things like "logic" and "rationality" have little bearing on actual market value.
Traditionally, morons who insisted on asking for moon money for common coins were weeded out via Darwinian natural selection: nobody bought their junk, so they starved to death. But the people asking for moon money on eBay are either (a) criminals using "rare coin sales" as a way to launder drug money and proceeds of crime, or (b) scammers who use the same basic principle as spammers and phishing: launch enough bait, and eventually you'll get a bite. Neither of those groups have any incentive to cease and desist.
Can eBay "fix it"? Sure, by re-introducing a per-listing fee. Just like e-mail spam would disappear overnight if the spammers were forced to actually pay a tiny fee per email sent.
