If you believe the gossips we have bid around £25m or so for him previous during the summer. Find it highly unlikely we will double that offer.
If they are interested in selling and we are interested in signing him I think something like £35m, closer to the end of the window feels more likely. Throw in another £10m when we win the CL or if he wins the Ballon d'Or, something pointless like that if it let's them save face.
If we are going to play 4-2-3-1 I'm not keen on him at all, if we go 4-3-3 them I'd happily take him, for the right price. And £50m is not the right price IMO.