Oh boy -- there is so much that goes into this.
Nobody here can just whip out a number for you, because we don't know your skill level, your experience, how much graphics work is involved (do they have a logo? do they have photos?) or how much of the site is already prepared (do they have copy already written? do they know what they even want on their site?!).
There are hundreds of quantitative variables, and still more qualitative/soft variables which don't have a precise value.
Web design is a whole industry. It's not a "hey, a friend asked me to whip this up" sort of thing. There are countless considerations and details. If you don't walk into it well-educated and strongly structured, and with a complete written contract, it's a 90% sure bet you will get burned. When
Andrew Neitlich and
the folks at Sitepoint talk about this stuff, they're not kidding. I didn't listen the first time, either -- and I also got burned. I wised up and bought
Brendon Sinclair's package. I'm glad I did -- it saved me from repeated disaster.
There are many decisions you need to make before ever firing up Photoshop or picking out a shopping cart system.
- How many drafts/revisions will the client get?
- Can the client demand a full redesign at one of your review stages, and not incur additional charges? (Answer here should be "no"!)
- How exactly do you define revision vs. redesign? You'll need those definitions to avoid being screwed into 100+ more hours of unpaid work.
- Who writes the copy? Who decides what should be involved?
- What happens if you, or them, doesn't meet a deadline? At what point does the project get "shelved" for your protection or theirs?
- Are you owed money for work done to date, if the client stops responding to your requests for information?
- Do they still owe you money if at Revision #2 they decide they don't like the work (even though you designed it exactly to their specs) and they don't want to pay you?
- Who owns the copyright on a partially-completed work?
- Who owns the copyright on a completed work?
And it goes on, and on, and on............. These are routine, everyday issues and common scenarios. Your contract is vitally important.
As for pricing, you should price based on value. This is not necessarily your perceived value, as we techies usually significantly undervalue ourselves.

What is the value as perceived by the client?
That is what you should charge.
By the same token, if you have zero graphics design skills, don't know the first thing about website navigation and design (or what makes a truly well-designed website)... well then you can't really charge a professional web designer rate. You have to cut your fees to make up for your lack of experience and skills. So then it becomes an exercise of at least trying to make enough cash to cover your time.
I'm not going to go deeply into specific site system recommendations, because I could write a book (in fact, I
am writing a book!

). I have had nothing but headaches with Mambo and Joomla. I use Wordpress for my blogs and like that a lot... but I would never put a
retailer on Wordpress... it doesn't display articles and pages the correct way for a fully functional website. Wordpress is blog software, it just hasn't yet made the jump to CMS. (I wish it would! I'm
eagerly waiting for the day...)
There are also webhosting plans which offer web-based HTML page editors. These work just fine, really. So if you have an HTML-making program (a good-quality one is
Contribute) the client can still edit their pages in the HTML page editor included with their hosting plan. So if you choose to write static pages, no problem. On the right hosting plan they can still edit them in a comfortable, familiar, WYSIWYG interface. It's seriously just like editing a Word document.
One thing that I like about starting the client out in HTML is that it is scalable.
Really! HTML pages can be "plugged in" in the future, to a shopping cart system like
OSCommerce or
Zencart. As well, HTML pages can have items for sale easily added through the use of
Mal's E-Commerce... that's how Mal's works. You just add items and his shopping cart code, to the static page. Voila! They're now selling.

Or, if they switch to a dynamic cart system (like OSC, Zencart, whatever) you can always copy/paste the pieces & parts of their current HTML pages into the new cart. The core work is already done, you just transfer it over to the new system. *shrug*
If they don't need prescise placement control of their individual items, then a CMS is fine. If they do need precise placement control of different individual items (one promos high-right on page 2, a different promo low-center on page 3, etc.) then static/HTML is the way to go.
Above all else though -- protect yourself so you aren't taken advantage of. They won't "mean" to take advantage of you... it's just a situation and an industry that is prone to people wanting everything at no additional cost -- or not understanding what is/is not included with the quote.

Bailey