They kept a player they wanted to keep. They will still sell Sancho for a strong fee when the time comes. I wouldn't really scrutinize Dortmund on transfers, they tend to do a very good job of flipping players for big amounts.
Did it? I would say its kind of up in the air. They are scraping for a UCL spot now, finances aren't good and are repeatedly aggravated and making comments in the media because the player they kept against his will is not performing to his own standards, now you are correct. they will sell him for a strong fee. But it wont be the 100+mil we offered last summer. a 100mil that would eliminate their financial stress. If they get less money for Sancho and finish outside UCL spots then the gamble was a bad one.