i would not say it would be stupid to go just for saturday. the saturday only ticket is $75 i think and 50%off with student ID. 4 day super ticket is $100. only thing you would be missing friday is testing and a big party. that and the race starts a 10:30Am so its nice to already be there not have to get up and drive over early. and if your anything like my your way to drunk to drive home after the race.
http://sebringraceway.com/ lots of good info on there website