Rumsey Rum Black Label

About 5s 0c on Beta · Horde (6 hours ago) and 2s 45c on Beta · Alliance (8 hours ago), from player scans. A vendor pays 50c, so the auction house pays 9.5× 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 10 brings about 47s 50c there, against 5s 0c at a vendor.