I prefer to look at AAV in terms of CH% rather than raw numbers.
McDavid's 2nd contract is a 16.67CH%
Crosby's 2nd contract was a 17.30CH%
But everyone thinks McDavid's contract is ridiculous and points to Crosby taking a "discount" on his 2nd contract. When taking the total salary cap into account (and base the calculation on caphit percentage instead), McDavid's cap hit is lower.
Now, let's look at Brady Skjei. If he signs an 8 year deal at 5m AAV, that comes down to a 6.66 CH% (salary cap currently at 75m*)
Taking a look at current top-pair D-men and what the cap hit on their 2nd contract was, it seems that a 6.66CH% is definitely not top pair money.
Roman Josi: 6.22
Ryan McDonagh: 7.31
Drew Doughty: 10.89
Erik Karlsson: 10.11
Victor Hedman: 10.79
Hampus Lindholm: 7.19
Aaron Ekblad: 10.27
Roman Josi has a very favorable contract for sure, but he is the exception. It's not as if 5 million at the current cap is 1st pairing money. If we sign Skjei to an 8-year extension at 5 million, it's a great deal down the line for a 2nd pair D-man (which seems to be his floor at the moment).
* While I use the current cap, it is expected the actual salary cap will be higher, lowering that CH% to a number between 6.4 (78m) and 6.09 (82m).