20m amortized over 5 years is worth it for a player you need.SMH. I wouldnt go more than that. If Dortmund dont want to play ball at that price I would be out and look at options. We still have other areas to address. he's not the final piece so it would be madness to spend that much on him.
And once you get rid of Smalling, Sanchez, Phil Jones, Rojo, Lingard, Pereira, Mata and Dalot there will be enough funds to address these positions.