Yes. There's the three year age difference. On the other hand Sanchez is much better. But I guess you are getting a younger player, there's no denying that.
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Because Real want to offload James (who has been consistently poor for them) and James prefers to join Bayern instead of us (if the rumours of us ever being interested are true). Also, Bayern simply don't need the money and don't have to sell players under market value.