Middle Eastern dune huntsman spiders, including some of the largest huntsman species known, discovered recently enough that the genus made news coverage this century.
They burrow in sand rather than flattening against bark, which separates their keeping from the family norm: deep fine sand, arid heat, and the same containment discipline every huntsman demands, because the speed is undiminished. Not medically serious.
Israeli and Jordanian dune endemism plus negligible captive breeding keeps supply near zero, and the genus trades as single-seller listings when it trades at all. Size is the product, scarcity is the structure, and the market is a handful of specialists deep.