The way I would justified my bikes (or any kind of excess spending for that matter):
1. I don't spend money on drugs.
2. I don't spend money on cigarettes.
2. I don't spend money on booze.
3. I don't spend money on fancy schmancy purses like Coach and such.
4. I don't spend money on male strip clubs.
5. I don't spend money on dying my hair or perms.
6. Make up is expensive and nasty.
7. I cook at home rather than go out to restaurants.
8. Cycling is healthy and low maintenance (not like a car)
9. You need equipment that will grow with you.
These can be applied to you (in the male version). So there. Justified?