Chris says that there's a consumer alert for a 512 GB microSD card for $6 incl. shipping. But as you can guess, that's a total ripoff because a name brand is over $100. Chris ordered one and it, indeed, was a fraudulent memory card. Complete counterfeits. Chris says that often, those cards are defects that have been "declared" as smaller cards, and sell them for cheap. The fraudsters get access to the broken cards and then reflashes them again to make them look larger than they are.
And here's a few tools on verifying if the card you bought is actually the card you wanted:
on Mac: f3 https://fight-flash-fraud.readthedocs.io/
1. Religiously test every card you use.
2. Return one that's broken
3. Stick with a brand you know to be good.