$33.50 for brand new MSI Gaming X RX 580 8GB:
http://www.ebay.com/itm/MSI-Radeon-RX-580-DirectX-12-RX-580-GAMING-X-8G-8GB-256-Bit-GDDR5-ETHEREUM-MINER-/322596953925?hash=item4b1c46df45:g:b88AAOSwmoBZbHwD

Looks like an anomaly due partly to some noob ending their auction after 2am with no min bid.  Live and learn. lol

Same item sold for $499 yesterday:
http://www.ebay.com/itm/MSI-Video-Card-RX-580-GAMING-X-8G-8GB-GDDR5-256Bit-PCI-Express-DL-DVI-D-HDMI-/222574172803?epid=781800439&hash=item33d2745a83:g:g70AAOSwjHdZYBU3

Locally, Craig's List doesn't have much except for one guy selling for $400.