Tokens do not appear to be on the xbox.com version of the Horizon 1 store page, so they might have actually removed them.
I think it's a waste of money, though. There are strategy guides and the like if you want the same content for free, just not on your actual map. I also don't remember having any need to grind, but it's been a long time.
Also, you're buying parts. It costs you money to downgrade because you don't own the lower grade parts. The "downgrade" is just a one button version of going through and manually buying the various mods and options. Horizon 2 did not do this because they just let you take any level car as long as it was the right type, which some people complained erases the progression path. I didn't mind either way, personally, but the way Horizon 1 handles it is closer to how Motorsport does. Basically, they changed from a stance of having only a certain number of cars at a certain power level available for any given race to letting you pick what car you want to drive at the level you want to drive it and tailoring the AI to that car. Both are valid design choices, I think.