I think price can be good between $5 to $10 . This is the nominal rate charged by service providers on different forums .
I just "hired" a friend to install WPMU for me. He didn't give me a price for the installation cause he said it was too easy for him and he doesn't know how much he would charge me.
How much should I give him for the installation?
I found a comment in a blog post about installing WPMU that says her hosting charges her $75. Must be a huge rip off then.
Here is the blog post.
Installing WordPress MU on a CPanel/WHM Server - Blogopreneur.com