To this laymans view, if it's illegal it's got a good chance of being unethical as well especially as a business plan.
(Sorry Peter, can't think of any other way to frame the argument well without resorting to laws
)
If the card was a stock...........the manipulator might be in some trouble.
From Wikipedia as iffy a source as it may be,
" During the dot-com era, when stock-market fever was at its height and many people spent significant amounts of time on stock Internet message boards, a 15-year-old named Jonathan Lebed showed how easy it was to use the Internet to run a successful pump and dump. Lebed bought penny stocks and then promoted them on message boards, pointing at the price increase. When other investors bought the stock, Lebed sold his for a profit, leaving the other investors holding the bag. He came to the attention of the U.S. Securities and Exchange Commission (SEC), which filed a civil suit against him alleging security manipulation. Lebed settled the charges by paying a fraction of his total gains. He neither admitted nor denied wrongdoing, but promised not to manipulate securities in the future."
And
https://en.wikipedia.org/wiki/Market_manipulation
That being said, I can't recall ever hearing of anyone in any hobby field getting in trouble for that sort of thing. Collusive bidding to keep prices down ? Yes. Shilling items to benefit themselves directly? Yep. Jacking up prices of other people's stuff to eventually benefit them selves? Nope.
So, maybe indifference, or the authorities don't consider collectibles as investment commodities, or it hasn't been done on a large enough scale to require a law or to have an existing one applied. And who would be in charge anyway? I can't see the SEC claiming they have authority in collectibles markets.
Steve B