In fact, a better way to explain this would be perhaps to use some hypothetical figures.
Let’s say hubby takes home £3,000 per month and his wife £2,000. The joint outgoings are £3,500. Most of the “big ticket” items of those outgoings (mortgage, utility bills, insurance, etc.) would probably not vary much whether there was one or two people. Hubby enjoys all the facilities of a home which he could not afford on his own whilst having £1,250 to spend each month. Meanwhile his wife, who has also enjoys the same facilities and has paid for half of everything (and probably does most of the housework – but that’s another argument), gets by on just £250. It’s almost as if she is being punished for earning so little and that’s no way for a marriage to thrive.