Depends if you're racing or not.

I probably spend a couple hundred in racing fees alone, about $250-$300 in fuel at least, a couple hundred for 4 nights accommodations and then probably $150 for food/drinks/alcohol.

Add about another $50 for miscellaneous and then whatever you end up spending on parts and I'd say you're looking at $850-$1000 on average, realistically, if you're racing every day (Friday night/Saturday/Sunday). If only spectating knock that down probably $200 between gas and racing fees.