Its relevant if you look at the team instead of just Subban.
You take Gomez' $7 million off the books. You can give $6 of it to Subban and leave $1 million to sign a scrub. Or you can pay $3.5 to Subban and have $3.5 to bring in a physical DMan or a player who can make an impact on offense. Giroux's (only using his name as reference for what $3.5ish million can bring) cap hit is $3.75.
So it becomes do we improve the team or do we improve PK's bank account?
I am positive that Bergevin is more concerned with the team than one single player.
But that's only looking at one year, and also at the highest possible price.
I have no problem going with a 3.5M, but if that's the case, expect PK to ask for double the amount if his development follows the same pace. And in 2years, you'll be kicking yourself in the nuts saying how we could have had him for much cheaper two years ago. You'll be back with cap issues as Emelin, Diaz, PK. For the bigger question marks, you also have Eller who's cash will depend on his progression, no way of knowing yet. There's Markov as well, if healthy and keeps playing as he has, should get a similar amount as he has now. Next year, there's also DD that is playing this season for big bucks.
So, the cap hell you're fearing might actually happen in 2 years, and you want to give PK a huge raise during that time, where he'll likely ask more then than he is now.
Just a bad idea.