Making some wild generalisations:

• Somehow we stumble across each other, you need a web site, I need more money.
• You give me a vague idea of what you think you want.
• I try to interpret what you meant and then decide I know best.
• A slow and painful process of me asking you questions and you thinking "Is it all worth it?" begins.
• The web site design evolves and your ideas become more concrete.
• I make the continual stream of changes you ask for and think "Is this ever going to end?"
• Suddenly it all comes together very quickly and we're all happy.
• Then I send you the bill, which you happily pay because it's a fantastic site.

This is what you want to know straight away, I can only say after finding out what you need. There are several factors involved:

• How large the site will be.
• How complex the site will be.
• How many different types of features you may want.
• How much time I have to spend on chasing you for copy, photos and feedback.
• How big my current credit card bill is.

From around £200 for a small site such as a personal blog, to £1500 and beyond for a large and more complex commercial site.
The average price is around £600, give or take.

I could say that you'll have a site that's HTML & CSS valid, cross browser compliant, Search Engine friendly etc. etc.

I expect what you're interested in is that your new web site will be....

• Something you're proud of!
• Impressing existing and potential clients.
• More upto date than your printed materials.
• Paying for it's self with increased sales (can't guarantee that one).