I worked out a budget the other day based on starting completely from scratch (inc. clothing tools etc.) and prepping a £2000 bike, and buying/insuring/taxing a £1000 van.
You're looking at approx £12,000 for you first season (If you start with nothing)
Now that IS terrifying for a 6 round race series on a cheapish bike.
Needless to say, I don't work it out that often - just about manage to find the pennies each time
...just!!