The time when these netminders also signed their deals is relevant. Both Gibson's and Hellebuyck's were in 2018, but some others were much older. Holtby's was signed in 2015, Schneider's in 2014, Crawford's in 2013, and Quick's way back in 2012. For reference, when Quick signed his deal in 2012, the 2012-13 cap was announced at $60 million. The cap now is $81.5 million. This means that Quick's $5.8M took up 9.66% of the cap back in 2012. In 2019-20 numbers, that same percentage would would be $7.87M per year. Salary inflation is a very real I think and it's important to take into account when finding comparables.
All that said, I don't see Marky getting much above $6M at most. He's been amazing, but goaltenders have been known to fluctuate quite a bit.