A tree on a street is incredibly expensive to maintain. The tree itself need maintaince from a gardner and the surrounding road and sidewalk needs extra maintenence too.
I remember only one incidence of the city being called in, or a private contractor to repair the sidewalk by the two oldest oaks on the bottom of the block whose roots had lifted and cracked the walkway. They just expanded the opening; I'm sure it was not up to code after for width between the areaway fence and the tree's opening in the sidewalk.
I can't believe it costs much to maintain them after the initial cost of planting them. I never had to care much for the trees on my property in NJ either, other than pruning some dead limbs that were about to fall over my access way or roof from the taller trees. The younger trees did fine on their own. Although, almost all of the hemlock trees succumbed to the Gypsy moths, but even neighbors who spent thousands on trying to save theirs, suffered almost the same number of losses. I was also not quick to cut them down if they didn't 'look' right. Now one that neighbors said looked dead, is thriving again!
I looked up prices as I was initially in doubt if this was a good cost-benefit. This article claims that New York Cty trees have a lifetime cost of ~3,500 USD (in gardening). I was under the impression of a much higher annual cost, so I was way off in my initial reasoning.
This report puts annual gardening costs of Portland trees at around 40usd [1]
These numbers do not include added road, curb and sidewalk maintenance incurred by the tree, as far as I can tell.
[0]http://scienceline.org/2013/10/the-high-cost-of-carbon-in-ci... [1] https://www.portlandoregon.gov/parks/article/514095
Pretty is nice but beauty without function gets old really quick.