Look, this isn't about whether the player is "worth" so and so amount of money. Do people really think Darren Bent is "worth" 22 million Euros?
People have got to realize that these are the current market conditions. The market is inflated right now due to the English clubs having much more demand than before, so the high price tag will naturally come around. So if you want something that is quality, you're going to have to pay for it, even if it's not subjectively "worth" what you think it's "worth."
Xabi Alonso is a good player, a player that we need, and 20 million Euros is probably a fair price for the player in these market conditions. I mean, he's damn good with the ball and has played well under pressure in Champions League finals and Cup finals, so I don't see what the problem is here.