exactly! it's very easy to cut your own hair, or if you can't manage that then hair plaited back or in a bun will look perfectly presentable and cost nothing.
Nobody is being denied a job (unless they work in modelling) because they haven't spent £180 having new hair extensions this month.
it's being pedantic to pick up on 'hair cut' as a necessity when it's been made perfectly obvious that it's anything beyond necessities, going into luxuries, where savings could be made. e.g. nobody is saying 'all these stupid people, if they just stopped eating and survived on air they'd save so much money,' but more like 'Actually if you stopped your weekly takeaway, or cut it to once a month or once a fortnight, you'd save £50 p/w which could add up to hundreds per year.'
If you're one of the people who have their takeaway and think 'ugh, that wasn't really that nice, the portion sizes keep getting smaller, it took ages to be delivered and was cold when it got here, I could make it myself much tastier,' then maybe it's worth considering. If you think 'No, my takeaway is my treat to myself after working hard all week, I really look forward to it,it's always delicious, we enjoy it as a family and not having to think about what to cook and clean up makes it 100% worth it,' then fair enough.