Everyone of us knew Salah, Mane and Firmino before they sign for Liverpool.
Great Scouting is too find Dybala in Argentina, p.e. Good scouting is too get Umtiti or Ter Stegen. Already good players but fit 100% in barça system. French and German markets are very good and affordable.
Why bother scouting if we buy Turan, Gomes and Mathieu? lol
Problem is that Dybala played 6449 minutes at mid-level team Palermo before going to Juventus, that's almost 72 full 90-min games.
I'm not saying this is the case with Dybala, but I'm sure there are plenty of players exceeding their potential thanks to regular playing time, as well as players not reaching their potential because of too much bench time.
For a club like Barça I believe the best thing to do is to buy from second tier clubs, like Lyon and Gladbach where the player has gotten playing time.