Wait until they start driving.....
Cars are one of the few things I can think of that would ever cost any significant amount of money (even college isn’t an issue for us because my wife is a college professor and our kids will get free tuition)
But there is no rule that states we have to pay for their cars. I know I worked and saved up for my first car, I see no reason why they couldn’t do the same. I could even save up their allowance for them that they earn from doing choirs and such and use that to buy them a car when they get older.