Even if Haaland will be a bad player for 30 Million is a good operation for the one who will get him.
With the money in the circus increasing every year, in 3 years you can easily sell at the same price or more (if he will fail).
If he will not fail and he will become a top player you can easily earn 50 Millions in 2 years.
Not necessarily. Barcelona bought Dembele for €125M and Coutinho for €140M. But no will pay even 75% of that in present market. Max both can draw 50% of their spending.
Similarly Jao Felix was hyped and sold for €126M but he doesn't worth that much, even on good days.
Players have to performance if they want their price tag go up or at least retain its value.
No doubt, €30M is a good deal for hyped player who is barely 19. But I don't think Salzburg will let Haaland go for anything below €50M and paying above €50M will be a bad business if he doesn't improve significantly.