Andy, editing is turned off after 30 minutes. You can just add another post to your thread to announce the price reduction, or contact Mike (Tyboo) or Bill (Da Nag) to see if they will turn edit on. Click the message icon, then type in their user names to send a msg.
As a generality, don't put the price in the Subject header as it cannot be changed by the member, put it in the body of your first post. Then if you want to change it make a new post as recommended above.