Dust of Deterioration

About 1s 0c on Beta · Alliance (2 hours ago), 20s 0c on Beta · Horde (8 hours ago), and 2s 0c on Beta · Horde (1 day ago), from player scans. A vendor pays 25c, so the auction house pays 3.8× 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 19s 0c there, against 5s 0c at a vendor.