It's not just a question of our absolute equity right now, but also how CO plays the different parts of his range. Almost half the time CO has AK, no flush draw, and gives up unimproved on the turn. So calling here is like paying $7.50 for a 50/50 chance of having the fish to ourselves in a huge pot where we have an overpair. Of course if the unknown CO doesn't c-bet AK no draw, then we should definitely fold now, but we don't know, and I think alot of people would.