OK, here's a stab at it:
Tires - $600/set mounted. Anywhere from 1 weekend to 4-6 races - they slow down, but they'll last if you're willing to keep running them. This item will have a big impact on your budget.
Consumables - Fuel (have to run leaded race fuel - grrrr!) ~$6/gal - I end up using 12-15 gallons for a national weekend w/ test day. Oil - I run RedLine 2-stroke - I use about 1 1/2 gal for the season (More or less - I don't really track it). The next-highest consumable would be the beer I drink while wrenching on it..... Theoretically, the belts are consumables, but I get pretty good life out of both - I think in terms of one of each belt for the season. Brake pads - how hard are you on brakes? I use a set of pads in 3-4 weekends - $40/axle.
Parts - I seem to go through rod ends - I have to replace 1 or 2 per weekend. The good part is that most of the F500 designs rely heavily on 3/8" rod ends, which aren't as expensive as the parger ones used on other cars. But, maybe that's why they fail more.... I also seem to beat up batteries and starter solenoids (still haven't figured out why). You will also need some clutch tuning parts and jets, but these are one-time purchases that might come with a car anyway. Bearings seem to hold up well, due to the low weight - they're inexpensive, standard industrial types anyway.
The cars weigh in at 800 lbs w/ driver (850 with the 493). Engines can run pretty long, depending on how careful you are with them. If you jet on the ragged edge, you'll be buying parts. There are guys running engines without touching them for several seasons, and there are guys rebuilding them once or twice each year.
For my weekend costs running National events:
$250 entry fee + $150-200 test day
$300 1/2 set tires (I use them for two weekends, then testing)
$100 fuel & oil
$150-200 fuel for the tow rig (distant events - less for the close tracks)
$150 hotel (for distant events where there are no relatives close by)
I end up budgeting $1000 per weekend, including incidentals and 'surprises', and it ends up being pretty close to that by the end of the season. I feel like $1000/weekend is almost a 'no excuses' level to operate these cars at. The only things I could spend money on to go faster are to run new tires every weekend, have a newer, more current chassis, and/or hire professional crew. You can certainly run competitively for less; you will pay more if you want to do an arrive & drive program.
Hope this helps....