If you paid $10,000 for something but could generally resell it for something like that value it wouldn't be a scam. But if you buy a $10,000 ring from a vendor and try to find a way to sell it for anything like that much, you will find you can not, and not only the usual "I can't recover the vendor guarantee and reputation premium" that you'll find if you try to sell things on Craigslist or something, but you'll find that you can't even come close.
It might be tempting to get into philosophical discussions about "what is value, really?", but that would be the wrong direction to go here. I'm happy to take value as a highly subjective judgment, because that is indeed what it is. My point here is brutally practical, and, well, exactly what I said, and no more... the problem here is literally that you will find that what you've bought can't be resold for anything like what you bought it for, and where that truth comes from doesn't much matter when you're trying to resell.
The art world is radically different. It is assumed that you are a smart consumer who is expected to defend themselves. And I'd also point out that if you spend a million dollars on something that turns out to be a really high quality forgery worth about $5K on the open market, we still call that a scam.