But only if you can sell it for more than you paid for it either above or under the table.
You can. Money laundering would use an "NFT sale" as a pretext to transfer large sums of money for some other reason.
Tony in Miami wants to buy $40 million worth of heroin from Carlos in Columbia. When Tony bank transfers the $40 million to Carlos, that's gonna raise eyebrows at the IRS and DEA. Tony needs a pretext. So he "buys" an NFT from Carlos to provide a reason for the bank transfer.