Well, I'm going to have to apologize to Bruins fans and eat crow here.
I made a proposal about 2 weeks back which was essentially two deals in one; one of which was Backes and Boston's 1st to San Jose in exchange for future considerations. This seemed pretty reasonable based on the precedent that I thought Kyle Dubas had set when he paid a 1st to get rid of Patrick Marleau's 6.25M salary last summer. Backes and Marleau are marginally different, but I think they're similar enough that they should have been worth a similar amount.
Then Don Sweeney goes and trades Backes and a 1st round pick, and gets Ondrej f***ing Kase in return. Unreal.
I have now officially learned a lesson that I should have learned when Mikko Rantanen signed for ~$1.5M less than Mitch Marner on the same term. Any deal made by Kyle Dubas does not set a precedent that will be used around the league.
EDIT: Things look a bit different with the news that Boston retained 25% of Backes' salary and tossed in Axel Andersson, but I stand by the point I made.