   Going prices for 2d 8-bit or 16-bit sprites
  like the above says. 
  Regardless of bit-depth the standard rate for professional sprite artists runs from about $15-$25/hour, depending on expertise and the size of company.  Amateur spriters vary, you''d have to get them to submit quotes on an individual basis.  Of course, you could always learn yourself, and then it''d be free... ;  go to pixelation.swoo.net and ask 