I don't think there's been a single area of disposable income that hasn't been subject to economising, post-parenthood.

SUPERMARKETS
Before: Tesco and Waitrose (for bits)
After: Tesco and Aldi (for bits)

CLOTHES
Before: White Stuff (yes, I sometimes dress like a wanker)
After: Sainsbury's

HOLIDAYS
Before: city breaks
After: tokens collected from local newspapers

GIGS
Before: monthly, on average
After: huh?

etc.

Give me some other examples.

*feel free to apply this to other life events