When you're hiring a professional photographer, you're not just hiring the photographer for the designated hours allocated for the photography session. The hours spent editing photos can be up to four times longer than the photography session. For example, if you hire a wedding photographer for 8 hours, it may take he or she as many as 32 hours to edit all of your photos. So while the agreed upon hours is 8, you're actually hiring he or she for a full 40-hour work week.
It should also be noted that every photographer edits at his or her own pace based on experience, style, and fastidiousness. But often if a photographer charges less, it usually means he or she is spending less time editing. However, similar to when you get your hair cut or styled, you want that photographer to take his or her time editing your photos because you want him or her to do a good job.
Below are two before and after examples of edited (color graded) photos. Notice how dramatic the improvements are of the edited photos.