Planet Money had a fun podcast a couple of days ago about Eric Meyer, the young founder of Haystack, a Baltimore-based app that allowed people to auction off their (public) parking spot to the highest bidder. MonkeyParking, a similar app, got attention last year in San Francisco.

The founders, in both cases, focused on the time-saving, traffic, and environmental benefits of such an app. Clearly there are real costs to people spending long periods of time circling the block in search of parking. UCLA economist Donald Shoup has argued that 30% of traffic in central business districts results from people looking for parking.

But these apps quickly generated enormous hostility. People used words like “disgusting,” “evil” and called it “JerkTech”—all to the apparent surprise of Meyer, at least. Within months, Boston and San Francisco had passed ordinances forbidding the selling of public parking spots. Haystack and MonkeyParking were basically shut down by the end of the year. (MonkeyParking has since retooled as a way to sell the parking in your driveway.)

This is a familiar story to economic sociologists. Some area of life that was previously outside of the market is suddenly brought into it. Violent feeling erupts, as such transactions are seen to challenge the moral order. (See Zelizer, Healy, Quinn, Chan, etc.) Generally, the market wins, and morality adapts.

There aren’t too many things—humans, organs (though even that’s eroding)—where a bright line still forbids buying and selling. Why, then, do Haystack and similar apps generate such hostility?

I think there are a couple of independent things prompting the hostile reaction.

1. Something that was, at least superficially, free, suddenly comes to cost money. People really don’t like being charged for things that used to be free, even if they were always paying for it somehow. (See: airline fees.)

2. Someone is making money by selling public property. This one is probably more important to city officials than city residents. From this perspective, the problem isn’t selling the spot, but who’s receiving the gains. Indeed, some of the same cities that reacted so negatively to these apps (I’m looking at you, San Francisco) have introduced dynamic pricing of parking, which allows prices to fluctuate with demand. (Think: Uber surge pricing.)

3. Now only the well-off can afford to park. This objection is to my mind the most legitimate. And while I fully recognize that it is really wasteful to have people circling around looking for parking, I don’t think it can easily be dismissed.

Now, I don’t want to stake any big claims around the inalienable right of Americans to park their cars. After all, you have to have a certain amount of money to have a car in the first place. And in general I think policies that discourage driving are good.

And it’s the very basis of capitalism to accept that there are things that some people can afford and others can’t, and to make one’s peace with that. But the thing about price caps (whether the cap is zero, as for street parking, or some flat rate, as with taxicabs) is that while they are inefficient, they are also democratizing. Yes, you may have to circle the block for 20 minutes. But dammit, so do the tech entrepreneurs who are pricing you out of your apartment. There are some things you can’t buy your way out of.

We live in a society in which inequality continues grow. At the same time, technology is improving our ability to make people who are willing (and able) to pay a lot do just that. That may be efficient. But it further reduces the sense that we’re all in this game together. And that’s the issue we don’t have a good solution for.