The Michigan Assessment is a pass through from the Michigan Catastrophic Claims Association and is set by them. There are some confusing comments out the trial lawyers about this issue. If you go straight to the source, http://www.michigancatastrophic.com/
"The 2010-2011 assessment is $143.09 per vehicle."
Michigan has the most generous insurance laws for these types of claims. Much like the upcoming budget battle, who and what gets paid for should be a subject of much debate.
Sounds like it's time to head to the nearest border and register/insure them out of state