Project Wonderful, Monetary gain or advertising?

I have project wonderful on my site and its usually full, Ive set all my prices to advertise on my site at 1 cent or free. Prices range from 1 cent up to 50 cents per day at the moment depending where the ad is situated and of course how much other people are bidding, In the past ive had people advertising that were paying $2 per day. I will put approximately 50% of my daily revenue back into advertising. I usually try and have a mix of sites that are with Entrecard as well as those that don't, this way it will bring new traffic.

My advice is to set your price low, Let the advertisers decide what they think your site is worth to advertise on, Ive seen many blogs that have a PR0 and an Alexa in the millions that are wanting 20 cents per day, And they wonder why people aren't advertising.

How many of you are with project wonderful? Do you treat project wonderful as revenue gaining or do you use it for advertising purposes? or maybe a bit of both?

There has been several other sites trying to do the same as project wonderful but seem to be failing (show your ad here and performancing ads) The only reason i can see for the failure is they have a minimum of $2.50 per month to advertise, This does not allow the advertiser to try before they buy, where as with project wonderful you can advertise for a day or even an hour to see how the ad is going to work for you before deciding on a longer term bid.