Centipedes, not spiders, and everything about them is different. Forty-plus species tracked, from the modest to S. gigantea, which reaches a foot and hunts vertebrates.
They are fast in a way tarantulas are not, they are strong enough to force poorly latched lids, and their venom is genuinely painful across the entire genus. There is no docile Scolopendra. Escape is the primary husbandry risk and it should drive every enclosure decision you make.
Most of the market is wild-caught, which is the key economic fact. Prices swing with import cycles rather than breeding success, availability is seasonal and unpredictable, and the same species can be common one quarter and absent the next. Captive breeding exists but is difficult and does not yet buffer supply. Expect volatility.