$389 -- Hawaii, R/T from St. Louis
http://www.travelzoo.com/Top20.asp?id=0256396
The rules on this fare are fairly restrictive compared to fares of just a few weeks ago. Here is the rundown:
7 day advance purchase is required. Hawaii travel requires a 3 day minimum stay. Travel to Hawaii is valid Monday through Wednesday. Travel from Hawaii is valid Tuesday through Thursday. All travel must be completed by February 13, 2002. Travel is not permitted on November 21, 24-26, December 21-23, 28-30, 2001 and Jan 2, 6 2002.