Also, it is NOT Dortmund's strategy to sell players. With every strong player that left they tried to keep him for at least 1 more year. They offered new deals with higher payment to Haaland, Bellingham, Sancho, and so on, so where would that make sense if they just want money. Dortmund wants success, they want to win titles.
If players want to move on for a big pay day and to a big name in European football you can't stop them. They have the power when their contract is expiring, nothing Dortmund can do.
Actually it is Dortmund's vision exactly. They don't prioritize becoming the champions in the Bundesliga. Instead they have a certain main vision that they have been maintaining for years. It is to bring young and talented players to the team for a cheap price and increase the speed of their development to make them young star players. After that they are okay to sell them for a really high amount of profit. These kind of players are using Dortmund as a steppingstone to join bigger teams.
Some of them push them to put a release clause on their contract as well though like Haaland did. This isn't good for Dortmund as they can sell them for higher amounts normally but there is nothing to do about it.