The biggest expense would be tires. I never had to buy tires, the regional and national series locally both ran different tires, so I would have to have a couple sets of tires, and rain tires for each race weekend. 5 sets x$200 is $1,000, other then a clone engine I haven’t purchased much during the past 3 seasons.
I think the expense of all the different rules, series, and classes is a big turn off. Hopefully some others will chime in, but are these regional and national events only to folks that are dedicated and are after competition? Does it turn from hobby to Pro driving at nationals? is it any fun?