I'm exactly the same, i'm a student with a part-time job, i always think carefully what my money gets spent on if its not for the car, like if i go to the pub i'm always thinking about how much i'm spending on drinks, even if im only having a few pints. Yet the other day i woke up and didn't think twice about buying a personalised plate for my car costing £250 and a set of strut braces costing £100
The thing is i get alot more enjoyment out of spending on the car rather than buying clothes, dvd's etc., so it doesn't bother me to much