I'd be willing to pay anything up to 20€ for Bathurst. Laguna Seca & Nordschleife.. Well, I don't think I'd be racing on them that much, after all Laguna Seca is just the corkscrew, and The Green Hell is just too hard to have competitive racing on it.
And paying for the tracks, the only way it could be done would be to donate the money. With that money the devs could then acquire the
license(s) and everyone would get the track(s). Paying for the track wouldn't work since it would without a doubt divide the community into smaller parts.
But I don't think there'll be any real tracks in LFS before the devs lose interest and open up the game for mods. In fact, I'm afraid getting the next new imaginary track into LFS might be years away