Well, I think it's going to fluctuate a bit, but the real problem is when people have too many ad-spots.. but that's usually a problem for the smaller sites.
I mean, I can;t afford to spend a whole lot on advertising, but since PW, I've spent a SHITLOAD of money on advertising I would otherwise NOT have spent... people lose track of mircopayments, and I think people are not being a little bot more intelligent about placing ads.
Personally, PW is awesome because price is ditacted by what the buyers deem as what they are worth. If ROCR's ads are low, it's because the people bidding don't feel that it's worth more right now. As a salesperson, you just have to deal with it.
As far as my own sites, It's a matter of opinion. I never really wanted to have ads EVER, and if I did It was just for webcomic promotion. So that is why I try to only approve webcomic ads on PSI... the things is, I'm not trying to have PW ads to make money, though it would be nice if everyone could break even and pass the money around. But that's me, but I also see what you are saying.
EDIT: also, because I like you and ROCR, and I know people will be visiting because of the Crossover Wars, I'm bidding on you mini Banners