If I file a complaint on a fake or damaged product on ebay or Amazon or the credit card company, I get my money back.
I assume Amazon/eBay are smart enouh not to send payments before 30 day period.
There's multiple ways that people make the scam work. Here's a common one for example:
The typical buyer isn't a suspicious STHer. If they can insert their card in a reader or camera and have it come back as "1TB" they call it good. And, through a combination of shenanigans and an absurdly high compression ratio, the card does report as 1TB. Its slow as hell, but as you noted, you can't expect the world for only $10. They don't even question why its already formatted, because they all come formatted these days.
They don't even have any issues, other than it being slow, until after they hit the actual capacity. Again, with compression, maybe that's even a significant percentage of the supposed capacity. And the seller is hoping when that does happen, the return window is closed.
But even when people do have issues, most won't think scam, after all they verified that it was 1TB! Some won't bother trying for a refund (its only $10!). Or they will try reformatting and assume that when it formats to 16GB, it has gone bad, because they'd verified it was 1TB when they got it!
Some might even get a refund. But most won't for one reason or another: return window closed, don't want to go to the bother, bought a bunch "just to have them" and didn't break into any for months, etc.
And even if the heat is on, the seller can just claim they got a bad batch and they promise they will stop selling them. Nobody at Amazon is going to do a forensic investigation for $10.