Here's the challenge I see.....
Jeremy Swayman has 3 years in the league as a true tandem goalie. Over those 3 years, he's averaged a .916 Sv% and 2.41 GAA on a team that most would consider good to excellent defensively.
Over that same time, as copared to other goalies in the league, he's ranked 6th in both Save percentage and GAA. Maybe you "knock him down" a bit because he's only played 122 games over the past 3 years, whereas guys like Saros (195 gp), Oettinger (164gp), Demko (147 gp), Vasilevsky (175 gp), Jarry (156 gp) and Bobrovsky (162 gp) have stats that aren't that much worse than his, and have played much bigger roles.
The B's have $8.5m in cap space... this shouldn't be that difficult. Do $8m x 7, or $7m x 5, and move on?
Given that the sides seem to be so far apart, it would lead me to believe that Swayman doesn't want to bet on himself at all, and wants to secure a $10m x 8 bag. That's a tough pill to swallow for a ton of teams.
I feel like Utah & Anaheim are the only somewhat reasonable targets. If in fact he wants that much money, he basically has to go to a bad team, as they're the only ones that can really bring on that hit, and live with the short term pain in hopes that the cap jumps.