I imagine what you're asking about is crossing the line between photographic services and graphic design services. I can't speak for the other commenters here, but I don't know enough about graphic design to give you advice on it. It took me 5 tries just to get my own logo designed right.
As far as your pricing, that's a question only you can answer. So many people on here want to know how to price their product. It all comes down to your CODB (cost of doing business), your COGS (cost of goods sold), your competition and the dynamics of your local market. We can't plug in those variables for you. Think about how much you need to make just to break even for your time, resources and efforts put into your client's work, and then build your profit margin based on what the market will bear. It's always a balancing act between pricing yourself high enough that you're respecting the value of your work and the industry, without pricing yourself out of a majority of your potential customers.
My nugget:
A while back I got frustrated with cheap, stupid people choosing Timmy the "photographer" with his new P.O.S. entry-level DSLR over me because Timmy is only charging them $12 for a portrait session and a DVD. I decided at that moment that I wasn't going to try to beat anyone on price. I'm going to do the research I suggested to you above, and not apologize one bit on price. I'm going to focus on delivering the absolute best product possible, so the client gets the maximum value for their investment with me. Beat your competition on value. Forget about price. Charge what you think is the right price, and if anyone asks you about it, tell them what I just said.
Hope that helps! Good luck with your clients!