I am not fully disagreeing with the above but the same is also true for many transfers in the summer too - the terms of a deal are dictated by a number of circumstantial factors, pertinent to that deal in particular.
You can overpay in the summer and the winter, just like you can make a great deal in either window too - there is no law/fact that would enforce overpaying on every single transfer in the winter, as opposed to the summer, for the sake of it being a winter transfer.
All in all, what I am saying is that words like "fact" should be used a lot more carefully.
you don't have to really