Perhaps the assessed value is low because the structure is in a flood plain and subject to fema 50% rule thus having no significant resale value.
All of the value is in the land.
Here's a listing of a waterfront cottage in our town that sold in 2022 as a teardown because of the fema 50% rule.
The house is still standing and was appraised at $125,200 and the 49 foot lot at $430,500. It sold for $575,000.
"The house is considered a tear-down - the true value is in the .12 acres of waterfront land. The interior, exterior and structural repairs are too extensive and would exceed the FEMA 50% rule."