How Much Should I Charge For A Link On My Homepage?

I just got the following question to my inbox: "How much do you charge for links on the home page of http://www.dietivity.com?" Here some stats: This site is getting about 200-300 visitors daily with a Google rank of three. My posts gear to specific questions a reader might have and are keyword optimized as possible. I try to keep advertising low... but now I've got this question to answer and I need your help... thank you:)