If the mountain contains valuable minerals then the cost will be negative; you can make money by removing it.

https://en.wikipedia.org/wiki/Mountaintop_removal_mining

Though, depending on the geology, you might not want to build a town on the resulting site. Sometimes heavy metals leach out of the disturbed rock, resulting in polluted surface water.

https://en.wikipedia.org/wiki/Acid_mine_drainage

https://en.wikipedia.org/wiki/Berkeley_Pit

It’s wild how many episodes have been edited or removed from circulation due to their content.

https://renandstimpy.fandom.com/wiki/List_of_banned/censored_episodes