Marketplace pricing — what should power 8+ gear actually cost?

Price discovery is still all over the place. I've seen near-identical power 8 rings sell for 40 GP and sit unsold at 400 GP on the same day. For anyone new to selling: a listing costs a flat 10 GP fee, the market takes a 5% tax on the sale, you can run up to 20 listings at once, and a listing can stay up for 30 days. So overpricing isn't free, but it's cheap enough that people try it constantly. What I'd like this thread to become is a rough community price guide. If you've bought or sold high-power wearables or components recently, post what moved and at what price: category, power level, price, and how long it took to sell.