With 1.44 sharpen requires 6 points of agility plus one more point for each point of sharpening over the basic level. So sharpening level 6 gets you a weapon that requires 11 points of agility plus the initial weapon requirement (give or take one point). Well worth it - my mages put enough points into agility that they can use sharpened short swords (the starter weapon for the deathknight - no minimum strength or agility) and as soon as they get the first battleground key I buy sharpening. They can then run around doing almost 100 points of damage with the shortswords, with almost no strength - which is a good thing since act 1 magic is so pathetic.
