I've extensively used both the ER4s and the ER-6i for many years now. They are easily the best noise canceling earbuds I've ever owned. They do an effective job of blocking harmful outside noise while providing a listening experience that even the most critical audiophile couldn't complain about. They also fit inside my helmet nicely! So, if the MC5 is anything like it's predecessors they'll be just as amazing.
...I believe they ran about $250 a few years ago.
Holy sticker shock Batman...new helmet, seat mod, half way to pipes, but earbuds/ phones???