I looked up publicly available player similarity data for Iafallo (courtesy of
De Lara Analytics), and these were the top 6 names that came up for his career through last season (April 2020).
If you check CapFriendly for these players' contracts signed at a similar age to Iafallo after this season:
Dzingel = 2 x $3.375M
Marleau = 3 x $4.167M into a 2 x $6.3M deal
Janmark = 1 x $2.25M
Bailey = 6 x $5M
Eberle = 6 x $6M
I think Iafallo is a better player than Dzingel, Janmark, and Kahun, and may be as effective though not nearly as productive as Eberle. Bailey is someone I wasn't as familiar with, but looking at his production he looks like a great comparable. Marleau is a funny one because that was so long ago in the early cap era that it almost isn't worth including. It would be cool to see what his comparables are including this season's data, as he appears on track to increase his PT/G total again this year.
Anyways, I think folks here are on the right track as far as Iafallo receiving more than $4M/year. If I'm his camp, I'm looking at that Josh Bailey contract. Their production is pretty comparable.