I can remember 10 years ago finding that most bargain cartridge games I bought were counterfeit (getting ones with typos in the name/description on the box art were my awakening) but worked fine. At that point someone might as well get a programmable cartridge and insert one's own memory cards.
> At that point someone might as well get a programmable cartridge and insert one's own memory cards.
I wouldn't be surprised if that's what some of the fake carts are. I ordered an X-in-1 card for DS recently (haven't seen one since the OG GameBoy days and was curious), and it was just a generic DS flashcart with a QA sticker covering the SD slot. Same seller was selling a bunch of single DS games without box and suspiciously cheap, so I wouldn't be surprised if they were essentially the same thing.