You can be on the first page for about .15 a click - but like Ramster says - unless youhave one hellofa conversion ratio with free surfers (like 1:30) it's not very targetted. On the other hand, if you have a way of earning that back on every click - go for it
BTW - that would put you around the 4th or 5th ad down on the first page - and about a cost of $55 a day for just around 500 clicks (estimated)