Blue Pearl

About 15s 0c on Beta · Horde (3 hours ago), 15s 0c on Beta · Horde (21 hours ago), and 20s 0c on Beta · Alliance (22 hours ago), from player scans. A vendor pays 50c, so the auction house pays 28.5× more.

1 recipe: Flash Bomb.

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 2g 85s there, against 10s 0c at a vendor.