I look at it this way...most coaches we know teach at more than one rink. There are probably 6 freestyle session they can get to - if they have enough kids. Let's say that they has every day booked. Sometimes kids are injured or sick or on vacation. If they work 5 days a week making $600 a day that is 3000 a week.
That is not unheard of for a "expert" in a specialized field.
At my job if my 'supplies' need to be replaced, my job pays for it. When dd's coach needs new skates, indirectly I pay for (a portion) it. Chances are if it is their only job they also pay for their own medical. I don't think $100 an hour is out of line. I can't afford that much so I don't select that coach, but I don't begrudge the coach who can have clients at that rate! They only charge what the market will bear.