A guy contibuting to an 85% PK is honestly providing just as much value as a guy contributing to a 25% PP.
stopping a goal is the same than creating one for sure, but in the term of value it goes with offer/demand, how many people are able to stop goals vs how many can create them.
And the value does not come from goal created and goal prevented, it come from goal created a cheap replacement player would not have created and a goal prevented the best AHLER would not have prevented.
as for the question in general if a team can sign a player and replace there current worst top 6 guy by someone that score.
1) 50 pts on the PK and playing no other minutes elsewhere, would add almost certainly 50+ goals to a team
2) 50 pts at EV, harder to say, but probably a small fraction of number 1
3) 50 pts on the PP, even less than 2.
Mario Lemieux arguably the best PP player of all time, missing but playing a lot of games during his prime can offer some windows.
The Penguins in 91-92 and 92-93 combined together (a rare example of a superstar missing (40) but also playing (124) a lot of games).
With Lemieux they scored 4.64 goals a games, without Lemieux they scored 3.38 goal a game
Lemieux scored 2.36 points a game to add a giant 1.26 goals a game to a team, more than half a goal by points.
The Penguins added .23 power play goal a game and 1.03 non power play goals a game.
Lemieux had .82 powerplay point a game versus 1.52 non power play point game.
It seem grossly that a
Lemieux PP point added .28 goals to is team, a non power play point added .677 goals to is team, more than twice.