Yesterday, Montgomery County Executive issued the first veto of his administration. It was of a major tax giveaway bill to developers — the county would likely lose over $400 million in revenue according to Elrich — passed in the name of sparking additional housing development around Metro.

My favorite part of the veto message in where Elrich, a progressive often accused of being an impractical lefty by opponents, explained the economics of these sorts of tax subsidies:

Under Federal law, WMATA must seek the highest and best price for their land. Land that is exempted from all property taxes for 15 years is more valuable because the calculation of its value includes the costs to acquire and develop, including taxes, weighed against market rents. If two properties are side by side, one exempt from taxes and the other not, and they were producing the same value of unit, the land value of the exempt property would be greater because its cost of development would be less than the cost to develop the tax-paying property. This would, in turn, likely raise the parcel’s appraised value. The Bill could potentially be counterproductive by raising the value of WMATA’s land.

Put another way, by reducing the tax burden, all the county has done is make WMATA’s land more valuable and increased the amount that they can charge for it. They will capture that value in the sale price of the land with Montgomery County taxpayers, who already heavily subsidize WMATA, having footed the bill.

They say you can’t get something for nothing. But if you’re not careful, you can get nothing for something. Or, at P.T. Barnum put it, “there’s a sucker born every minute.”