They are free, Nature gives them to us as a gift.
In terms of damage caused a tornado can cost anywhere from nothing, if it simply tears across open country to hundreds of millions of dollars in the very worst cases. At least four tornadoes are known to have caused over $1 billion in damage. More may be included in this group if you adjust for inflation.
tornadoes don't cost anything they just happen, but the cost of the damage might cost millions
The Greensburg tornado cost about $250 million.
The cost of damage from the Waco tornado was $41 million.
Damage from the Tri-State tornado is estimated to be $16.5 million in 1925 amounts.
The Joplin tornado caused about $2.8 billion worth of damage to the city of Joplin.
NOAA resources say $16.5 million worth of damage was caused by the tornado, but it does not specify if that is modern amounts or the amount in 1925.
The costliest tornado on record was the Joplin, Missouri tornado of May 22, 2011 with a cost of damage at $2.8 billion.
Its Free
5 billion dollars
Probably about £35 million each
This varies by each incident and location.
That depends on which tornado you are referring to. St Louis has been hit by many tornadoes. The St. Louis tornado of 1896 had a cost of about $20 million at the time, which is equivalent to a bout $570 million in modern amounts. The St. Louis tornado of 1927 cost about $22 million at the time, equivalent to about $300 million today. The St. Louis tornado of 2011 had a cost of about $30 million.
The most famous tornado today is most likely the Oklahoma City tornado of May 3, 1999. That tornado caused approximately $1 billion in damage.