On one of the people per hour websites I was recently amazed to see someone offering the first 5 pages of proof reading for $20 with the implication that this was a really good offer. It seems very expensive to me.
Maybe I’m under charging at £20 per hour?
Obviously speed depends on the subject matter to a certain extent; I have proof read some fairly complex subjects from theology and philosophy to medical theses and they will take longer than say a creative story. Another factor that will impact on speed is the amount needing correction. If one is proof reading work from someone who does not have English as a first language there will be a certain amount of grammatical correction to be done as well as checking for normal typos.
I seem to notice more typos in novels these days – maybe proof reading is a dying art!