I finally convinced my pet tank to get back into the game as well.
Since he's not averse to buying things from the cash shop, he bought a lockbox key after some questing and opened one of the boxes in his inventory.
It got him a drake mount.
He immediately bound it to himself, but I looked it up on the auction house and there was only one for sale, for the price of five million astral diamonds. Lucky bugger!
(This was also the first time I saw someone I know trigger one of those admin announcements about people winning rare lockbox prizes. Initially it didn't even register with either of us since we're so used to ignoring them, but then I just had to scroll back up to take a screenshot.)