I think you have to look at the sort of club Salzburg are when judging them on these contracts and buyout clauses. They're trying to establish themselves as a decent European side - they have money but they cannot attract established high level players to the Austrian League. Their answer has been to target promising youngsters with the promise of regular football. These promising youngsters are willing to join Salzburg because they're given a chance to develop and most importantly, they see a clear pathway from Salzburg to bigger European clubs. Without these buyout clauses, the pathway to bigger and better things isn't there and Salzburg won't be able to sign these players in the first place.