Not bothered at all. Bayern can make these gambles considering that they have also the likes of Martinez, Thiago and Vidal in midfield. If the transfer doesn't work, they will lose 35m euros, but the results won't get affected. However if we bought him for a lot of money and the transfer doesn't work, then we would have lost money in addition to having to play Fellaini in midfield.
I don't want us to sign young players for a shitload of money, unless they are pretty much stars in the making, like Martial. Sanches can go either way, and isn't an attacker in the first place to command that much money. The beneficial thing on signing young players is that they cost cheap, but if you have to pay 35m (+45m in add ons), then it isn't a very shrewd business IMO.
Also, not all big money transfers from Portuguese League work, and as efficient as Bayern are, not each transfer they make works well. Still think that Bayern have made a very risky signing, which could go either way. I would much prefer if we go for a more safe transfer, considering that we need to improve the squad immediately, not 5 years down the line.