Well, whether he turns out to be a good or a bad signing will obviously depend on how he performs for us over time (whether he will turn out a good signing has feck all to do with the price, in short, unless one thinks the transfer significantly impacted our ability to get future transfers done). Did he make sense as a right sort of signing - would be a more pertinent question. He's fairly young, he's a good player, he has certain traits people have been crying out for (and which, presumably, Ole and his staff were looking for too).
You seem - like many others - to be very concerned about the price, which is understandable given how much he actually cost (compare him to VVD and it looks like a shite transfer - sure). However, I don't see this as a case of splashing an insane amount on a player who objectively isn't worth it at the detriment of further recruitment (in other areas). There are good reasons to think we would have coughed up plenty more this summer if certain deals could have been done (but that wasn't to be, for one reason or another). So, I'm not too worried about the money. We needed a CB, he fit the profile and we paid what we had to pay in order to get him. We can keep saying "he isn't an 80m defender" - or we can judge him on what he actually brings to the table.
As for long-term impact, he's 26 and could realistically be a useful player for us for a number of years. Sell-on value is pretty much irrelevant, I would say.