Madrid are genius at selling players.
CR7 is still CR7 but 100 M for a 34 y.o player is still incredible. They made a mad profit on Morata after buying him back from Juve, they managed to sell PSG a singer that has football as an hobby (i.e. Jesé) for 25 M.
I'm sure they can make a profit on Mariano while he barely played for them. Think they can sell any player for an high price, just because of the Real brand.
Its not genius, its stupidity actually, seeing as we bought pretty much no one to replace these players(Mariano doesnt count).