I think the industry standard is something like 0.1% click through rate (1 in 1000 people will click on your banner). I don’t see how this can be a good return on investment. Even if 1 of 1000 click on the banner, statistics are not on your side. 90% of the people who click will stay on your site for less than 5 seconds. This is fine. You might still want to continue and spend money on them. But the thing is no one is going to talk about a banner. When was the last time someone told you about the funny banner they’ve clicked on last night? Banner will not create word of mouth and you won’t get more for your buck. Banners are not experiences and if you do decide to go for them, just remember that your dollar is not working for you. It’s sunbathing.