I think Bob Mckenzie of tsn said it best. He said Montreal likes, maybe really likes Subban but don't love him. And you have to love someone at 8-9+ per year for long term.
The other part that was mentioned is Carey Price's contract. Montreal consider him their best and most important player and he makes 6.5M per year. I don't think they are willing to lay someone more than that or at least not as much as PK seems to want.
I hope we sign him because he's exciting to watch and so good on the power play but I won't cry if we trade him and get something good in return and we would because he has great value.