My city spends ~$20M/y on the fire department [1] and has ~300 structure fires and ~14k callouts annually [2]. The cost for a marginal fire is definitely not millions; even if you only divide $20M by 300 you get $70k and that ignores the tens of thousands of other calls they take.

[1] https://stories.opengov.com/somervillema/published/BhSqQ0eG2

[2] https://www.mass.gov/doc/2020-county-profiles/download