Right, so Mathieu is 31 (29th of October 83) and Luis, as you phrase it, isn't even 29 yet (August 9, 85). Ya, way to bend fucking reality and logic to further your point, buddy.
Anyhow, the Luis and Mathieu transfers are hardly comparable. We don't need a LB starter, we need a utility man who can play both LB and CB. Mathieu can exactly that. Is his value 20M? No, not by usual standards, but we all know how screwed we are, and the opposition clubs knows as well. Hence our predicament. We pay up, or we move on. Simple as.
Oh, and one more thing. You argue that Mathieu can't possibly be good enough, because he's not on the NT. Using that (dumbass) logic, why don't you feel to mention Luis' current national team status?