Lightning Eel

About 21c on Beta · Alliance (7 hours ago) and 55c on Beta · Horde (8 hours ago), from player scans. A vendor pays 10c, so the auction house pays 2× more.

No. It is in Classic Era too, with the same item level, vendor price and stack size.

Sell it on the auction house. After the 5% cut a stack of 20 brings about 3s 99c there, against 2s 0c at a vendor.