I don't know the $75 race. I haven't done Battenkill ($95?) but I could see the appeal. I tell people you'll either get a rider just once or multiple times.
One time rider - goes there, doesn't place, has a mechanical, uses up a whole weekend and has negative memories.
Multiple time rider - goes there, doesn't place, has a mechanical, uses up a whole weekend, and has positive memories. Wants to return and do better, even if it's improving from 102nd to 89th. Customizes bike for event (wheels, tires, possibly bar position or whole bike, etc).
If it's part of an experience, it's one thing; like triathlons or running races - very few people enter thinking they'll win anything. It's just improving on the previous performance. If you enter to win, well, that's a different story.
I'd do a Battenkill kind of race if it suited me a bit more (a hard race is one thing - a death march is another). If I really liked it I'd try different things. I kind of held an unofficial kind of race like that (it was free though):
http://carpediemracing.org/shartkozawa2008.html (when bridge work cut the course in half - last year it happened)
http://carpediemracing.org/shartkozawa2006.html ("full" course)