Here is the low key, Evening Post, page 16, Dec 1, 1973 press clipping that announced the introduction of the DPB.
"The new benefit will provide all solo parents, irrespective of the cause of solo parenthood, with defined benefit criteria; rates and income exemptions," said Mr King (Minister of Social Welfare).
The next is the Hansard from 25 October, 1972, which shows Hon. L.R. Adams-Schneider, Minister of Social Welfare (soon to be replaced by a Labour government Minister as per above) detailing the expected cost of the DPB.
"The cost of the proposed domestic purposes benefit is estimated at up to $250,000 a year."
Adjusting for benefit inflation, that's around $4 million by today's standards.
So what is the bill for today's DPB recipients? $2.3 billion