I've asked this question and so have you. Did you get the right answer? That depends if you asked the right question. I always counter with, "How will you use the image or what is the purpose of the session?"
A US passport photo session. This has specific requirements. I know the size, lighting, paper, number of images, pose, expression, cost, and it takes about 10 minutes...$20
An executive headshot session. This is in the studio with onsite proofing and simple retouching...$100 Multiple images for branding purposes...$150-$250
Family portraits with 4-6 people, multiple backgrounds, different clothing setups, mixed groupings--may take 45 minutes to 2 hours; then, the family may want different pieces and sizes of albums or wall art which again will alter the cost to...$150-$$$$
An old-fashioned protestant church wedding. This photography session can start and finish in a few hours; but, the family may want a custom album or two, and wall art...$500-$$$$ ???
An exotic location wedding. This photography session can last a few days, require multiple shooters, air travel, hotel rooms and the family will probably want multiple albums and wall art...$$$$-$$$$$
Commercial photography. This session can be on location or in the Studio. There may be specific art and layout requirements for advertising--along with time, models, materials, and usage licensing for publication uses...$$$-$$$$$$$
The point is, the photographer you hire should ask a lot of questions to deal with these situations. The professional needs that I have for a passport session, are very different to the needs for a newborn baby session. So ask a lot of questions and think about the answers given to you. If you think the cost is too high or low, ask why. The bottom line is how you feel when you look at your images. Will they make you smile? Perhaps they will make your business look strong and reliable. Perhaps they will speak of openness and trust. Perhaps they will make you cry with memories from that day. If you hire a Pro, they explain the costs, times, and details so you both will be happy with the final product!