It's a lot of cap.
That said, he's 26, and you gotta hop the cap starts rising in the coming years. Our offense is pretty young for the most part and it shouldn't be too hard to keep the major pieces together...guys like AA, Mantha, Larkin, etc. aren't going to be getting major caphits for some years to come. By that point we should be rid of some of those terrible contracts we have.
Our offense with Stamkos + the guys we have, assuming they come somewhat close to their potential, looks pretty good. You combine that with Mrazek and we're not in terrible shape. We still lack D, but we have assets to trade for some help and that help combined with the offense + goaltending HOPEFULLY makes us an attractive destination for some help through free agency in the coming years.