Would this Champ Car sim be an entirely new game or an rFactor mod? I presume an entirely new game having learnt about your job and work/pleasure trips to the US recently.
I personally think the price I would pay for a game would depend on how it was distributed. If it was like rFactor, LFS and netKar Pro then maybe about $40, but if it was on CD/DVDs then about $45-50.
If however the game was quite exhaustive in its replication of the Champ Car series in having multiple seasons, editors and modding tools provided etc then I would be prepared to pay around $55-65 however the game was distributed.
I love playing GP4 and now rFactor, LFS and soon netKar Pro. I haven't gotten into Champ Cars but having looked up the site for the series I think I would like it and would really enjoy having a game to introduce me to another form of open-seater racing formula and perhaps leading me to try to watch some Champ Car races.