This all depends on the sites throughput and its knowledge of previous per click revenues. If it's a large site then expect very big prices..my partner works for a company that has a top ranking (google no1) website that attains over 6 million unique visitors per day, they allow advertising and for a third tear very small advert/banner (you have to navigate through three seperate levels before you would see it) they charge €700 per month. They are very well orgonised though and are constantly being contacted by potential comapnies wishing to use all available space, so much so that they are completely booked up for at least 12mths in advance.
The cost for first tear advert space on the said site is just not worth thinking about. The reason I know about all this is because I cheekily enquired about having a link to here on their site. As you can tell, I shelved the idea once I found out the costs.
