So I was curious and did the numbers...
You have a household income of £24k/year split £18k/6k
-your DH is paying £1800 income tax/NI per year and you are paying £0
-with 5 kids, you get £20,000/year in benefits (assuming no savings and no disabilities). That's £300 Universal Credit, £35 mortgage support, £87 child benefit per week
-no student debt repayments if you went to Uni since both under the threashold
-mortgage in £75k house over 25 years assiming 3.6% interest costs £4200/year
That leaves you a household income after tax and mortgage of £38k/year or £3200/month
The fictional family on £100k/year split £60k/£40k
-pays £25k/year income tax/NI
-no benefits, not even child benefit since one earner is in the higher tax band.
-student debt repayments (Uni degree needed for professional jobs earning £40k+) £4350
-Mortgage on £350k house (more expensive area where those jobs are located) over 25 years assiming 3.6% interest costs £21,500/year
That leaves this 'unimaginably rich' household income of £50k/year or £4200/month after tax and mortgage.
That's £1000 per month more than your family: £4200/month vs £3200/month. Nice, but hardly enough to buy a house per year!!!
To be honest, I'm actually quite shocked that there is so little difference. No wonder the UK has such a bad productivity problem, with 20% of working age adults not working and a further 20% working part time.
If the higher earner decides to half her hours, their household spending money (after tax and mortgage) will only come down by 25% to £33k/year (ie same as yours!). She might well decide that's a worthwhile sacrifice to have more time with her kids/look after her health.
Unfortunately, the net amount they're putting into the common pot drops from 29k/year to 15k/year. So where will the 18k/year your family is being given from the common pot come from?
But at that point they have the same amount of disposable income as your family. If they realise, maybe they'll sell up, move to Durham and fulfil their long-standing ambitions to become a teaching assistant on 18k and a school lunchtime assistant on 6k. Very worthwhile professions, and why wouldn't they given that they'll be no worse off financially?!?
Pretty disastrous for the economy though.