I am always sitting between $19mil and $20. I nickel and dime tuning parts when I need them. I can't get myself to drop all 20mil on a car...maybe I should, but, ugh, soooo much grinding.
I'm at 18 million atm, usually I'm around 15-20m, buying all the car I dont have + some color variation for the cars I like. I try not to "waste" the money and always buy something when I'm at 20 millions, got all the pricy car already.