Its a lot closer than you think honestly. Rask signed his deal in the summer of 2013. Up to that point:
138GP / 2.15 GAA / .927 SV% / 16 SO / 59.6 GSAA
The season isn't over yet and Swayman as of today:
122GP / 2.32 GAA / .920 SV% / 12 SO / 47.3 GSAA
If reports of $7 million are true, then it'd be an 8% cap hit (assuming $87.5 million). Rask's deal was a CH% of 10.89% when he signed. To put that into the cap into perspective for next season, Swayman would be making about $9.5 million to be equal to what Rask got. I'd say all in all at $7 million that's a solid deal for Swayman.