Perhaps we just desperately want the money in and don't want to drag it out until the end of the window, or jeopardise losing the transfer altogether.
I agree though, £15m would be robbery in the current market and we should be looking at least £25m.
Have to say though, I'm surprised Man Utd are interested, I can't see Arsenal spending a chunk of their 'alleged' small budget on him, plus Leicester have just signed Tielemans so can't see them getting him as well.