I can't think of anywhere else in the world that values draft picks and defencemen more than HF boards.
I mean Karlsson is an excellent player, but he was just traded for a typical trade deadline rental haul and now he is worth Austin Mathews.
The return for Karlsson shows his value. Every team around the league would have been able to make an offer.
Then I guess Chris Pronger, with a lengthy contract, was worth just Lupul, Smid, and a 1st right? Never mind the fact that Edmonton would never have traded him if they really had a choice, because you don't move a player like that because you want to.
The high price of defensemen has already been established. It's been long established, and is constantly reinforced every year. One outlier deal, and one where no one thinks Ottawa got good value out of Karlsson doesn't change that. That's a fallacy.
No GM's are going to look at this deal as the new standard for elite defensemen. There are no phone calls happening right now where some GM is calling up, say, Nashville and saying "We can offer you more for Subban than Karlsson got." or Tampa Bay and saying "Have I got a great offer for Hedman!" It's not happening. I don't think you really believe that's the case either, so this is just you trying to defend your player through absurdity.