I don't know anything about these events...
How do you end up getting to go?
Is it the kind of thing that they pay you to attend, or is it like being in a garage band or a marathon runner and you pay for the privilege of participating?
Are there qualifiers?
I'd imagine that there has to be some kind of restraint on participating, performance or price -wise, else you'd have all kinds of gag entries. Grandpa's station wagon, mom's minivan, etc.
Other than getting cars and people to the hill, what's involved?