Here's a great explanation from photographers Lin and Jirsa:
http://www.linandjirsa.com/hiring-uncle-joe/
Tell us what you think. Do you still prefer Uncle Joe to take your pictures?

I found an interesting article from a fellow photographer who replied to a person on Craigslist who thinks that photographers' prices are "wack". I believe it's worth reading it so you have a better understanding of all the work and preparation required to ensure that you end up with the best photographs posible because those memories are supposed to last a lifetime. Here it is:
http://www.petapixel.com/2012/01/26/why-wedding-photographers-prices-are-wack/