I've done a great many video voice-overs, both in recording studios and with my own equipment. My experience covers pretty well everything from business documentary to video games, including YouTube, advertising pitches, poetry readings and audio books.
My voice is a gentle, mature baritone (if desired, I could send a couple of samples), my accent is neutral English with a Celtic (Irish) tinge.
As I have no idea how long your video will be, nor what the subject-matter is, I can only guess that the finished recording will not be longer that one hour and that the script will not have to be edited.
If this is the case, my bid could be reduced to $440. Anything that requires more time and effort than, say, 10 hours, would of course be negotiable.