NFTs have value solely because some people agree that they do. The same principle applies to money - bitcoin, dollars, dollar bills, etcetera. It doesn't cost anywhere near $100 to produce a $100 bill.
Unlike a physical good that is priced near the cost of its production, abstractions such as coins, NFTs and the like are not inherently valuable. They are only valuable because some people agree that they are.
Most of economics is just a shared dream/delusion that we have found to be useful.