I charge $5 for character designs, regardless of how many sketches it takes.
$10 to $20 on comic pages, the former for inks, latter for full inks and colors.
$20 for pinups.
$30-100 for pencil drawing, depends on content.
Prices are completely negotiable.
Here is a link to my gallery here: http://www.conceptart.org/?artist=Crazedms20
and on deviantart, which has my comic: Crazedms20.deviantart.com