Well Ok maybe I'm wrong in taking in taking starting bids as my thread's "backbone" but it was meant only as something close to actual, how am I supposed to know how much was spent in banner ads, if theymos keeps deleting the posts.
At any rate that just shows how much signature ads may be effective than banner ads, so now the situation would be: You got 3 btc to spend on ad, you can either make a sig ad with 15 of the best posters on the forum and give them 0.2 each month at a fixed rate of 0.01 per post, max 20 posts.
Or you can buy banner ad slot at that amount and still have only 1/10 chances of being shown, not taking into consideration that most people use AdBlock extension nowadays