Dortmund football club is just following their pattern of business and that is the way that they profit in the sports business. You cannot tell them to abandon their method. In the German Bundesliga, we can attest that Bayern Munich has dominated all the trophies for more than a decade. So grooming of young players and selling them at exorbitant prices is the way that Dortmund will prosper and make their money. That was exactly what Wenger was doing in England with Arsenal because they were unable to contents with average players he needed to groom them sell them and make money for the club.
You're right over the years that's what they've been known for,from Lewandowksi to the current Jude Bellingham that's been very Fantastic for Realmadrid and is currently their star player, they're good at buying young prospects for a cheaper fee, develop them into future stars then sell them for a huge fee to top European clubs and over the years they've been successful in it and has cashed in on their young stars.
This season they still got young talented players that they could benefit from financially next summer and one player I believe one player that could really succeed this season is Karim Adeyemi, he performed brilliantly last season but has not really been very impressive due to the teams performance but individually he's a good player and does it brilliantly for his team and when the team bounce back to full form, we'll see the best of Adeyemi this season.