How much damage can tornados do?

It varies widely. Some tornadoes stay in open fields and cause not damage. Weak tornadoes (EF0 or EF1) cause minor to moderate damage, damaging roofs, breaking Windows, and overturning trailers.

The most violent tornadoes (EF4 or EF5) are devastating. Well built houses are completely demolished. In some cases entire neighborhoods can be flattened. Damage can be in the hundreds of millions of dollars with some exceeding $1 billion.