I probably hear this from people more than anything else.  The conversation generally goes like this -

Client: I need a website.
Me: What type of site are you looking for?
Client: Something really simple, how much will it cost?

Well, not to try and read the mind of my client, but this is generally a way of the client saying they don't want to pay too much for their site :).  Seriously though, the general misconception is a simple design doesn't take a lot of time and therefore should be inexpensive.  This is more often than not, not the case.  If you look at any Fortune 500 company's logo I can guarantee you it looks fairly simple.  I can also guarantee that that company spent a lot of money to make it look that way.  Simplicity sells for many reasons and when it comes to websites simplicity is most important for ease of navigation throughout your website.  If your website is cluttered your customers will be unable to find what they are looking for.

Now a simple clean design like this e-commerce site we did about a year ago, may appear simple but by no means is a "quick and dirty" $500 website.  The e-commerce programming that lives underneath the shell was very costly and time consuming.  In fact this was the very first website that utilized the Cart 2.0 e-commerce software that we created.  This site took over 6 months to build even though the basic design was complete in about 2 weeks.  Of course now that Cart 2.0 is complete we can complete an e-commerce site in the same 2 weeks. Some important things to remember when thinking about your site is how much programming will be necessary.  Programming can be as simple as a contact form and as complex as e-commerce functionality or massive database programming.  These types of things on a website are not always something that you "see", but they can take the most time and cost the most money.  And as far as things you can "see", flash animations and video can take a long time and add a great deal of cost to your bottom line cost of developing a website.

I am working on a website now that I will highlight in a blog post when complete.  For this particular website we were hired for a complete video production on location in New Jersey.  We hired a voiceover artist and spent a lot of time behind the mixing board.  Bottom line - this video will take up a space on the homepage at about 320 x 240 (its really small folks).  This is just one example of adding a small element that adds significant cost to website development.

The bottom line is know what you're getting into when planning out your website and sometimes small things may be small, but quite time consuming and expensive.