Originally Posted by Barefootsies

No clue. I think it would depend more on click throughs to better gauge an asking price. Banner, or spots on a site are worthless unless they actually generate some traffic.

I'd guess sell a spot to someone for what you think is fair for a month, put some kinda tracking code on there so you can see traffic generated, and then you will have the numbers to justify your asking price for the following month.