Of course it is a joke, it is Terry Pratchett after all.

But there is a serious problem behind it.

For example, with food, if you have enough money you can afford to buy large quantities and take advantage of discounts.

For rent, it you have money, deposits won't be a problem, and landlord may be more willing to give you interesting offers. Poor people are at risk of not being able to pay the rent, and landlords have to account for it. You may even buy and not pay the rent.

For utilities, if you have money, you can buy more efficient heaters and appliances, better isolation, maybe even solar panels and stuff like that which may be profitable after a few years.