I don't see how this makes sense at all for Montreal. I think we can all agree, getting a 4/5 Dman isn't difficult via FA at roughly 2.5-4M. Montreal also has enough on their current roster so this isn't a need.
Montreal would be far better to retain 40% on Price and receive actual assets that can help their rebuild, rather than an overpaid player who would just block players who are the strength of their prospect pool (LHD). Retaining on Price allows them to spend the money saved on an actual need.
The determination that Price is "declining" and therefore is worthless, seems to totally ignore the fact he carried an inferior team to the finals just last year. Sure, he's not worth his contract, but he can still play at a high level.
For the record, I don't think Montreal would retain that much on Price, but hypothetically it would be a better option than Vlassic.