there was a report on motocross here just like that, it was a "new sport" the funny thing was they showed pics of the track back in the early seventies at the end of the report.
I don't know man, I have put maybe $500 into my set up so far and that includes buying the parts truck....if you have friends with benders and welders, and you know how to do alot of the things your self you would be suprised how far you could get on how little you spend. I have friends with all the parts you could ever want just sitting in fields rotting, and I pretty much just tell them what I need and we work something out.
71 Bronco - twin sticked, full width, 2" lift, wristed arm, lots of rust...