Sure, inflation and purchasing power parity calculations don't always work between very different societies, but if you replace that indicative £1000 sum with "sufficient to ensure you can rent enough land to put a teepee on and buy some of the basic foodstuffs you can't hunt/forage any more" which is what Paine argued civilization had cost the average person, it doesn't start to look like an adequate welfare replacement.
He does say, "That price does not include windows, door, insulation or interior furnishings. In place of a brick fireplace I have recommended a recycled steel barrel stove and stove kit from Vogelzang that would be more efficient."
Those things he is excluding will easily double the price. A wood stove costs thousands, maybe hundreds used. 8 sqft of insulation is $50. Windows are $200 each. A door the same or more. And also, 10'x15' isn't really viable for a home, even for one person, much less a family that wants a shower in the bathroom.
We also have building codes now that require a functional kitchen and bathroom which add significantly to the price of a livable structure the government won't tear down.
I think bare minimum costs to build a livable structure today, would be in the $50,000 range and the mortgage on that would be $300 per month, which would fit within my proposed living stipend of $2,000 per month per family of 4.
You'll easily pay $800 for one of these stoves, used -- in the summer. Which is why I was saying that you can just use an inflation calculator to figure out how much things cost today relative to yesterday. We have better technology, more building codes to follow, and more things to buy.
Life does cost more today than it did back then, more than inflation can account for.