add between $0.6 - $1 billion in value
The way I understand it, that's not the key piece of information - in fact by itself it's kind of misleading since that's not net of the cost that has to be invested to produce that benefit.
The point of the article is that you have to spend something pretty close to that amount, potentially even more than that, to get that benefit - which is not exactly an economic miracle. And that money that has to come from somewhere (aka someone). And as far as I understand, the analysis (haven't read in detail) doesn't take account of the opportunity cost, i.e. what alternative benefit might be achieved by spending that money in completely different ways, including leaving it entirely in the private economy.
Tell me if I'm wrong.