The first 10 races a player participates in every day are at the base price of 10,000 tokens. After that, each additional race costs 20% more (12,000 tokens for race #11, 14,400 tokens for race #12, etc).
Overpaying for races will earn you credits towards the Mechanic Mastermind game mode which allows players to build new vehicles, only if they build upon their knowledge with each guess