Except Hedman's contract isn't underpaid though. There were two reasons he signed that deal, no state income tax in Florida, and 7 million aav allows Tampa to keep their core together.
If you want to get caught up in the optics of $9 million vs $6.5 million that's fine, but there are other things to consider. You have to remember the 6.5 would have been 8 years instead of 7 that NJ signed. The longer the contract the less the aav should be. And when you compare NC's state taxes to NJ's for his salary, 6.5 and 9 aren't as far apart as you think.
Also, at $9 million aav for a defenseman Dougie's age, it is an aav that does not hold up well. You look at defenseman in their early-mid 30's making high dollar, including a player currently on NJ's roster, either/both the contract is seeing as terrible or the player is on a non-contending team. In fact, of all defensmen making over 8 million aav, only 3 of them are on teams considered contenders (Makar/Carlson/Pietrangelo), and they are much more of a #1 than in my opinion Dougie is. And you have to remember with Carolina, Dougie was playing #3 minutes in games that mattered, which makes 9 aav insane.
And yes, Skjei's contract, even though he is a top 4 pairing dman, is high for his overall production. But two things to consider is Carolina didn't sign him to that contract, NYR did, and he'll only be 30 years old when the contract expires in 3 years. Also, that is ultimately a movable contract if it came down to it, although I don't think he's going anywhere at this point. And yes, the Gardiner contract is painful. He was signed after the team decided to move on from Calvin Da Haan after he had shoulder problems, and the contract looked bad after year 1 of 4, which was a point I made in Hurricanes threads about the risk of signing Dougie for too high of a dollar for too long.