This is again assuming that the person who fills that $50k/year job contributes exactly $50k/year in value to the economy.

And at some point, when you are talking about investing public funds to create jobs in a period of high unemployment, you need to think of it in terms of subtracting the cost of that person's potential unemployment benefits, medicaid, and other costs that an unemployed person imposes on the public.

So, it's kind of complicated to do a full cost/benefit analysis of this.