Pocket nines have better edge on an AK, let's think a bit, you have 99 and he has AK (in pre flop), there are still 48 cards left on the deck, and 6 of those cards will give him the better hand, and the other 42 will guarantee a win for pocket nines (discarding the chanes of a straight or two pair made on the table, which is a very small chance). So pocket pair is always ahead of two overcards, then it's profitable in the long run, but in the short term anything can happen.