If the double race (Sat and Sun) format gets attention, consider this:

Entry 1 race on Sun (weekend pass) $70 ($10 discount) includes 2 time runs on Sat
Entry for 2 races (weekend pass) $70+$80 (promotor makes up for Sat discount with 2 entry fees, same payout on Sat and Sun)

That gives the hard core racers two races, but gives the casual racer a chance to come out without spending a lot of money.