Margins on most runes are thin now.
My position on "flipping" is that it's a great way to make money while you don't play. You spend 3 minutes doing this when you first log in, then 3 more minutes when you first log out. Rest of your time you can spend playing the game, and the market works for you while you are away from game.
I don't make a ton this way, but a little, and it's easy and doesn't take much time to juggle, say, 10 items.