Unadjusted List
1. Katrina 80-200 Billion (2005)
2. Andrew 26 Billion (1992)
3. Charley 15 Billion (2004)
4. Ivan 14 Billion (17??) (2004)
5. Wilma 12 Billion (2005)
6. Rita 9 Billion (2005)
7. Frances 8.9 Billion (2004)
8. Hugo 7 Billion (1989)
9. Jeanne 6.9 Billion (2004)
10. Allison 5 Billion (2001)
11. Floyd 4.5 Billion (1999)
12. Isabel 3.3 Billion (2003)
13. Fran 3.1 Billion (1996)
14. Opal 3.0 Billion (1995)
15. Frederick 2.3 Billion (1979)
16. Dennis 2.2 Billion (2005)
17. Agnes 2.1 Billion (1972)
18. Alicia 2.0 Billion (1983)
19. Bob 1.5 Billion (1991)
20. Juan 1.4 Billion (1985)
Adjusted List
1. Katrina 80-200 Billion (2005)
2. Andrew 43 Billion (1992)
3. Charley 15 Billion (2004)
4. Ivan 14 Billion (17??) (2004)
5. Hugo 12.3 Billion (1989)
6. Wilma 12.2 Billion (2005)
7. Agnes 11.3 Billion (1972)
8. Betsy 10.8 Billion (1965)
9. Rita 9 Billion (2005)
10. Frances 8.9 Billion (2004)
11. Camille 8.8 Billion (1969)
12. Diane 7 Billion (1955)
13. Jeanne 6.9 Billion (2004)
14. Frederick 6.3 Billion (1979)
15. 1938 6 Billion (1938)
16. Allison 5.8 Billion (2001)
17. Floyd 5.7 Billion (1999)
18. 1944 5.8 Billion (1944)
19. Fran 4.5 Billion (1996)
20. Alicia 4.4 Billion (1983)
WOW

All information taken from National Hurricane Center website
http://www.nhc.noaa.gov/pastcost.shtml