Do the math: how much would you have to sell each month to make back your $20? How many clicks would you have to get before someone makes a purchase? How well are any other advertisements you have on your blog doing currently? A banner ad is a very passive form of advertising, and I'm guessing you'd have to have A LOT of traffic to convert enough sales to make up your $20 each month.
at 11:06 AM on Jul. 2, 2011