Donny some are free, some 99 cents, $1.99 and I've seen some for $9.99. The few that I use have been either free or $1.99. YOu can get a better idea if you visit the iTunes store via the iTunes interface.
http://www.apple.com/iphone/apps-for-iphone/

[This message has been edited by Stephenm52 (edited 11-04-2009).]