There is nothing wrong with doing business in the football industry and that is what they do to make a profit. If the business is run like the one run by the owner of Dortmund, they will never achieve the club's achievements. The reason is that they only focus on selling players and never try to buy quality players at high prices. A trophy is a big hope for any club, but if the club does not have a supporting force of quality players then it will be difficult for them to achieve it.
Football clubs are not just there for entertainment but they are also for their business dealings and I do believe this is why Dortmund sold this incredible player at some point, fast forward back to when Arsen Wenger was in Arsenal as the head coach, this was a kind of business Arsenal football club was into, grooming of players and selling them when they are at their best to raise money for the club.