According to the AFTRA (American Federation of Television and Radio Artists), the first hour of voiceover is paid $346 and $101 for ea additional half-hour. At least that's what I got a year ago. You should check AFTRA's website and see the newest rates for supervision. Also, not every agency or company is a Union member, therefore their prices need not be the same...
Thanks for the suggestion, Linda. I do not see any rates mentioned for supervision, only those corresponding to the voiceover talent. Am I missing something?