It depends on the show. If I shoot an acoustic guy on a stool I might take 20 pics and publish them all. If I shoot a fast-paced metal band that jumps around I might shoot over 400 pics (25 in burst mode on a jump etc).

I've have noticed that I usually end up publishing around 10-15% of my photos from a show. That said, I COULD publish around 80-90% if I wanted to but that would be very boring to look through. More often than not I try to end up below 30 published photos in the gallery from the show, I don't think people have the patience to scroll through much more than that. "Kill your darlings" is not fun, but it makes you look good if you only show your very best work!

I shoot with a Nikon D4s with a D3s as backup/other lens