From Degods (SOL NFT):
They called it a PHBT (Paper-handed bitch tax) where any time an NFT was listed below its previous selling price, it would be taxed at 33.3%. This is a great idea because it creates a stronger floor price (in theory) as people will be less willing to sell since the loss will be more significant. The team could use the funds from the tax in any way they see fit.
My ideas would be: Burn the $TUS from the tax. Use as potential rewards in Arena mode. Use $TUS to buy back crabs that will fall under the same 33.3% tax, and burn them/auction them/use a rewards. Plenty more options, just thought I would list a few.