The best way to check if a card is legit or fake is to try to fill it up and see if it holds the contents. I recently got a 256gb card and I had a doubt that it was fake so I started copying 8gb folders again and again and after 2 tries it started deleting the older ones to make space for the new ones, turned out it was a 16gb chinese card that shows 256gb size programmatically. A tool to do the same is H2testw, it copies random data to card and reads back after filling it up telling you how much was lost and what was retained.
I would suggest buying memory cards from AliExpress, I have bought two 128gb cards for about $28 CAD each, write speed is 90MB/s and cards are legit, using one of them in vita now, had no problem, also bought sd2vita from there, everything works flawlessly. Can take a bit longer to arrive but saves you a lot of money and headache.
