Duke political scientist Michael Munger (an eminent public choice theorist), compares tax expenditures to the Catholic Church’s selling of indulgences.
Indulgences were “get out of purgatory free!” cards. Of course, it was the church that had created the idea of purgatory in the first place. Then the church granted itself the power to release souls from purgatory (for a significant fee, of course). …
We let people out of tax purgatory if they own large houses, if they receive expensive health insurance from their employer, if they produce sugar or ethanol, or any of thousands of special categories. These categories have nothing to do with need (is there a national defense justification for a protected sugar industry?), but instead depend on how much these sinners are willing to pay to members of Congress.
Another way to look at it is as price discrimination. Or were indulgences just an example of that?