And they would have provided markets for lots of goods and services and would have filled the labor rolls, to say nothing of their missing contributions to the arts & sciences. Think about their contributions to Social Security — we’d all be better off.
I don’t find it particularly useful to think of such things. The benefit a sovereign human being may or may not provide to a government program or an economy is only relevant if humans were to be subjects or serfs existing for others or for a government.
The argument is best framed in terms of that sovereign human’s right to life, liberty and pursuit of happiness endowed by their Creator. Their utility to others is irrelevant.