As always gotta say I agree with DonAndres. Realistically all of those players aren't going to be baught in 1 season. I agree with most of the sales people have mentioned but I think only Valdes (7-10 mil), Afellay (9-12 mil), Alexis (18-22 mil I hope!), and depending on how management treat David Villa from here on he could leave for 8 to 12 mil. If David and Alexis go then I can see a new striker coming in. If either stay then no but if they go I think Aguero, Cavani, Falcao are out of the price range. Suarez could come for 30 mil and as I much as I like his skills he is a bit of an immature ass. Lukaku is a young versatile striker if Chelsea would sell.
Realistically I don't see Hummels leaving Dortmund. Maybe Vertonghen because he hasn't featured much for Spurs but then thats also why management might not go for him. Alderweireld is another bright Belgian on the rise and took over at Ajax where Vertonghen left off. He's versatile and strong. Another "tested" option I think we have is Sakho who is pretty solid.
As far as a goal keeper I have been really impressed with De Gea lately. He's young, tall (6'4), speaks Spanish, and plays for ManU who play a lot more high profile matches compared to Monchengladbach. Ter Stegen also hasn't looked that good lately. Lloris is highly unlikely as Spurs baught him for the future and Courtois is probably going to replace Cech soon.
All in all GK: 17 mil CB: 15 mil Fw: 20 mil could happen this summer. (on a side note it will be nice to have Blaugrana stripe home and Senyera away jerseys)