The only issue I have with this is that, AFAIK, the city is offering you this information for free. I can understand if you were paying a licensing fee to have access to the location data, you'd want to cover that fee. But wrapping up a stream of data someone else produces and curates doesn't justify a recurring fee to me.
You'd be surprised at how ugly the data we get provided is. The "curating" is actually much of the work we do. We probably spent as much time developing internal tools that clean and improve that data that on the app itself.
Server costs and continued development also are recurring expenses. Like I said, we might have gone down a different path if Apple allowed paid upgrades, but they don't.
