46 mio or how much the deal was worth is really good business from Bayerns perspective - Costa is not worth more than that really.
We have aging wingers, but he couldnt manage to bench anyone of them which speak quite clear about his time here. Not to sound like an arrogant fuck, but the winger system have been used in Bayern for a very long time where Its relative new in Juventus. When you have been used to having the likes of Robbery you simply need someone to take over who have the same vision and Intelligence as them on the field. Costa didnt show that here.
Its fine he is doing great for you guys, but wingers here are expected to have something more. It will be difficult to find the right Robbery replacements, even though Coman is doing a great job atm. Costa is not the answer for our wings, else he would still be here and have benched Ribery long time ago for good.
But all the best to him in Juventus.