So I lurk on the Duggarsnark subreddit and someone posted about income, which I thought applied to the Radfords as well. According to this persons thorough calculations, for a family of 22 people to live just above the poverty line they'd need to be making 217k in America, which is about 156k in british pounds. To live a middle class life (decent cars, occasional holidays) they'd need 350k, about 251k in gbp. The radfords live in a pretty cheap area but they clearly live a rich persons lifestyle, so they'd need to be making far far more than 250 thousand pounds a year for the 18 children at home (19 until recently) plus Ophelia and the two parents.
I know it's been said over and over and it's nothing new now, but 30k a year is utter rubbish.