I have a site set up with 3 categories and view a list of courses for the site settings--so it brings up the course titles with little icons. (See image--this is a case where an enrollment key is given to employees for some things, but they have to pay for other stuff).
I have added to the course>lib.php file so that if a course has a cost, it will put up a $ icon instead of the key icon. (will submit it next post).
The problem is for some reason I couldn't get it to read the requirespayment string for the mouseover on the icon (so have just added the text for now). If somebody wants to check into that it would be helpful. Otherwise, you can use this code as is.