My neighbor says it’s about $100 to run the first race and then about 40/race after that. You have to join the district you want to race in.
The few I watched last year had skill levels from me(barely able to keep the bike on 2 wheels) to just incredible riders.
If my kid gets into it, i will probably start racing them next year.
check out www.adrenalinevision.com My kids love watching the races on this site.