Rune of Portals

About 8s 0c on Beta · Horde (21 hours ago) and 50s 0c on Beta · Alliance (22 hours ago), from player scans. A vendor pays 5s 0c, so the auction house pays 1.5× 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 76s 0c there, against 50s 0c at a vendor.