I don't think they can afford it, i think it's all an illusion that they like others to perceive. They are floating above water just by the skin off their teeth. If they were really as popular as they make out and as rich as they like others to believe, why have they no Nanny, no PA, no cleaner, don't pay for days out, don't pay for holidays etc. etc.. because they had to cut costs.
They make enough to keep afloat but there's no way they'll sustain it for much longer.
She Shops from Occado or whatever it's called to make it look like she's posh, but look at the other aspects of their lives, they cut corners in every way possible.
Credit is a great thing to give the illusion of riches. Materialistic things are all that matters to them to fake great wealth. But car rentals and free clothes and products from companies keep them looking like they're rich.
I don't for one minute believe they're rich or even close to it.