You are talking about us being wrong for signing talented teenagers. When we first eyed ronaldo together with Manure he hasn't even played regularly in the Portugese league. He was just a talented teenager as well.
Compare this to Niang, he played 2 full seasons, one in ligue 2 and one in ligue 1.
Its always good to sign as many talented youngsters as possible, any one of them turns out to be a world class player we'd have saved a huge load of money. The others we can always sell for good fees. See Vela.