Sebastian Haller has joined Borussia Dortmund and is back to Bundesliga after a fairly decent run with Eintracht Frankfurt and after being kinda poor with West ham. Revitalized his career at Ajax with 32 goals in 50 appearances. With much more attacking prowess that Borussia brings. He should thrive there.
Borussia Dortmund are used to losing some of their professional players because this club is often dubbed as a printer of new players who have high expertise, so because they often get offers to buy players with very high nominal, so it has become a normal thing for them.
Dortmund management does not spend too much money to buy players. They find talented players. And makes the utmost effort to make these players experienced. At the end of the season they make money by selling these players at very high prices. I believe Dortmund will be able to make a lot of money selling Sebastian Haller in the next few seasons.