So your point is that academies are useless?
Even if you have the cash to buy X player, fans love to see a homegrown youngster break into the first team.
It's a completely different feeling as a fan, when you see a 19 or 20 year old take his first steps with the main XI, as you know deep down that this kid was produced by your academy
As for your example about Fabregas and Pique....from what I recall, it was Fabregas' choice to join Arsenal (even though Barca wanted to keep him) and Pique chose Manchester United when he was 16...because Barca could not offer him a professional contract at that age.