Well. An important aspect of this is figuring out the company, small business vs larger business.
So I will go with 2 different ideas here based upon what you will be working with.
1st I am going to go with the small business idea.
You have two main things to work on here. Credit Card system and the Page design.
Depending on the work you have to do for this you could charge from $50 to $500. This is a broad area. If you have to design some storage system for orders and such and have to track the status then you would be looking more at the $500 range. If you simply have to execute the verisign script it could be as little as $50.
Next is the individual page design. For this a rough estimate would be $300. If you spend more time working with DHTML and a lot of images the price goes up. But for a simple clean design you can get away with $300.
For the current economy you need money, they don't have money. You could get away with changing them $500 for a complete job. It doesn't appear too hard on paper. Maybe 5 hours of work, maybe 10 hours of work. It really depends. If you can get it done in 5 hours your making $100 per hour. If you can get it done in 10 hours your making $50 per hour, which is not a bad rate.
If it will take you longer charge proportionally. I don't like to go much under $50 per hour worth of work, but at the same time I have worked for $10 per hour just to get some extra work. One of my % jobs ended up paying me about $1 per hour. So it is kinda open to what your willing to work for. Figure that out and go from there.
The other thing that is kind of static for me is my $50 per month retainer fee, for up to 4 hours of maintainence per month. An additional $50 per hour over that per month. Unless they pay the retainer fee I delete all the .psd files and all my code from my computer.
If you are working for a larger firm who knows what money is and how to spend it your price can go up quite a bit. Although you will probabally be putting much more into it. A good starting point would be $100 per page to layout. $300 for the site design. $500 for the site scripting. $100 for setting up registration.
Then you package it as a nice round figure of $1099.99 and pass it to them with the nice disclaimer of maintainance and the itemized evaluation of the specks.
The might not be the best way, but a good idea is to again go with the standard rate you want and then add from 20% to %50 to the bill. Corporations tend to be slower at getting you information so you have to charge for these lags.
This is all general. Pricing can be hard. You really have to know how long it will take you and what you time is worth. My time I like to think is worth $50 and hour for my design and coding work, but I am happy to work for $15 if it pays the bills. Doc on the other hand works at $250 per hour. It is a tough area here.