I think a good place to go for a "baseline" cost would be: http://99designs.com/ http://99designs.com/ I used them for some graphics work at my current employ

I think a good place to go for a "baseline" cost would be: http://99designs.com/ http://99designs.com/ I used them for some graphics work at my current employer and was happy with the results. It at least gives you a starting point and a place to negotiate from.