The most expensive German football transfers of all time: Germany's most expensive assets

13th place: Mats Hummels 16/17 for 35 million euros from Borussia Dortmund to Bayern Munich

"If you can't beat them, join them," Mats Hummels probably thought when he returned to his former youth club in Munich after eight years at BVB. However, he wasn't entirely happy at Bayern and returned to Dortmund after three years.