If you think tax subsidies have anything to do with EROI (i.e. EROEI) you are very confused. This is calculated on the basis of Wh/Wh. Simple dimensional analysis shows that $ doesn't show up at all in the calculation.
Of course tax subsidies are useful to bootstrap on a $ cost basis, but with current costs and rate of falling costs even that will soon become unnecessary (let's get rid of fossil fuel subsidies to make this "real world data" comparison fair though).
Cash flows are in fact a reasonable proxy for energy in many cases. Manually tallying up the uses of energy and materials is a handwaving exercise at best, but net losses of cash in the energy industry indicate with certainty that you not yielding net energy to society as an enterprise.
Of course tax subsidies are useful to bootstrap on a $ cost basis, but with current costs and rate of falling costs even that will soon become unnecessary (let's get rid of fossil fuel subsidies to make this "real world data" comparison fair though).