Real Madrid has never had financial issues the last time I remember and they had experienced growth due to the trophies they won in the last 5 years so right now it they have decided to start making profit with buying and selling of players like the Dortmund team you mentioned I hope they don't sell their star players like Dortmund and start getting the issues of underperformance and not being able to win trophies. If Real Madrid could focus on the business and still be dominating in the game and continue winning trophies then it's a good one for the team.
Real Madrid have always been dominating and topping the chart for the most profit made in club football, we shouldn’t even compare the two clubs, because Real Madrid have the ability to attract even big names and small names and it is the small names that they develop and sell off not that they will sell there big names like the way Dortmund does there business. Should Madrid ever sell off there big players it will be for a more bigger player
The success behind the Real Madrid finance is Florentino Pérez because all the time he made so many great decisions to make the team finance. This all credit goes to him, whether it's about bringing a big player or selling some of the team players. The real secret of the club's success is that you adopt that method which can improve the club state. Not like the president of Barcelona, who just spends big fee and big wages even if he gets banned later. Perez even said goodbye to Ronaldo when he demanded high wages. So it is true that Perez's transfer skill is outstanding, like he signs top players for zero fee, i.e. Kylian Mbappe.