do the math. - truggy ->
1 tank = 150ml = ~10 minutes = ~900ml (~1 quart) per hour
czech nationals - 5x qualifier = 5x5+3 = 40minutes, 1/4 final 15+3 = 18minutes, 1/2 final 20+3=23minutes and if lucky
30+3final = 33 = total 114minutes so about 2litres of fuel x 6 races per season = 12liters or about 3 gallons x two clases
then of course ton of other races with some of them being 3x10+3 qual = 33minutes + 20minute final so about hour of runtime 5 time a season
it really depends how many races you plan to run and fuel cost is the least to worry about. all the travel expenses (car fuel, accommodation), car parts, tires are way more
yes it is quite expensive hobby