Races at this level are expensive to put on. Good for them for charging appropriate fees.
By way of comparison, I entered WMOC 2018 yesterday and it was EUR 130 (which, if my memory serves me correctly, is at the low end of the range for recent WMOCs).
I mean, yes, they are expensive, but then again the Loppet Foundation has plenty of experience putting on races and for the races which are taking place on these trails (no road crossings, busing, police details, etc) the cost seems rather high. One of the reasons I'm not going out to the Cities for these races. The snow is getting made there and the trail maintained whether they have these races or not. The marginal cost of putting on the race is relatively low. (For someone flying in from Europe, EUR200 is probably a minimal cost. For me, it would be as much as the airfare, or close to it.)