The mechanism that the "right people" communicate which minting wallets are the "legit" ones. I.e. even in the less-crazy levels (i.e. not thousands of dollars), you'll see artists announce their wallet key on Twitter/Instagram/their website, and it's on the buyer to check that what they buy has the right source. (If people think that your bootleg mickey mouse NFT has value and pay for it, well that's their decision, they just might not find anyone who agrees later)