At ProPhotoForum.com recently a new topic was posted by Rob Hoffman that casts some light at this tricky issue. So rush and read the topic "How to price your photographs". Actually there is even more than just prices - there you can find about business expenses and how to factor them into your pricing. So this topic could very well fit into your business plan

Posting prices on the website?
In another topic Rob gives his opinion about that:
My personal thoughts on publishing my prices on the web are not to do it. This is something that can be debated to death, but I don't put my prices on the web because I want to avoid people shopping just for price. I feel that if I can get them on the phone and then into the studio for a visit, the value of my work and what they will be getting will provide the necessary motivation to retain me based on quality not price. Now, that being said, many people will argue that you will be passed over if you don't list prices on the web. In my personal experience I don't want clients that have to ask "how much?" right away. You know the saying, "If you have to ask, it is too much"---well that may apply to me personally and my clients generally are not driven to me by price, but by a quality or service they are seeking. Again though, many will say that their prices are one of the features they choose to highlight because to them it is a selling point of theirs---they feel potential clients will see a great value based on numbers alone----I think it comes down to a personal decision of the type of client you are looking to attract.