Lee Sin have to buy sightstone only...

when he's playing on LCS. Forget about this item in soloQ, you have trinket for 250 gold. If you don't agree - check your Lee Sin winrate with sighstone and without it. Sightstone moves you far behind in damage, but in LCS its ok, because their Lee Sins have Uzis and Doublelifts in their teams. Good luck, and don't forget that pro 5v5 games is a different world comparing to soloQ, and many pros said it many times: "in soloQ we're no building like on pro-scene".