I'm going to combine Guentzel's regular season and playoff stats, which essentially combine into 2 regular seasons. That puts him at 61 goals and 123 points in 159 games, which turns into 31 goals and 63 points per 82 games. Even just looking at this year, he had 32 goals and 69 points in 94 games, which turns into a pace of 28 goals and 60 points per 82 games. So I think it's fair to compare him to 30-30 players, which includes guys like Palmieri. The best comparables I can find for Guentzel are:
Wennberg: 6 years at $4.9 million, after getting 13 goals and 59 points in 80 games at age 22
Nyquist: 4 years at $4.75 million, after getting 27 goals and 54 points in 82 games at age 25
Trocheck: 6 years at $4.75 million, after getting 25 goals and 53 points in 82 games at age 23
I think you're looking at a Trocheck type of contract for Guentzel, I think that's a really good comparable for him. I think the players who get a lot more than that (such as Huberdeau) were either super high draft picks or they had a lot more NHL experience than Guentzel. Huberdeau, for example, had 5 years of NHL experience when he got his $5.9 million AAV extension and also was a #3 pick overall back in the day. He also won the Calder in his rookie year.
I think the draft pick factor is a big factor here, because you pretty commonly see higher draft picks getting a lot of money or shorter term on their first deals.