We have some new features for Shipping settings due to roll out soon, but as of right this moment, I think the closest we can get to what you describe would necessarily have to charge more for each add'l CD on Int'l than for Domestic shipments, rather than the flat $1 extra per CD regardless of destination that you described. You may find it helpful to know the basic formula we follow when calculating shipping charges:
((cost per oz.) X (total product wt. + container wt.)) + (container cost) + (handling cost)
The (cost per oz.) part would be determined either by a flat per-oz. rate you specify for Domestic or International shipping, or otherwise by standard USPS rates if you have your zipcode entered without any custom rates in Seller Admin > Cart Shipping Settings (we compare USPS First Class vs. Priority and apply whichever rate is cheaper). Note that you can "game" the formula by applying non-literal figures for various settings, so the formula adds up the way you want. Also note that the Tube container types can consolidate various products into a single parcel, whereas the other containers all assume each product would be shipped separately.
I think this approach should be fairly close to what you described:
* Log into your E-junkie Seller Admin > Cart Shipping Settings;
* Delete your zipcode (which will disable USPS ounce-rates);
* Set your Domestic rate to 1.00, and your International rate to 2.00;
* Set your Handling charge (lower right corner) to $0.00;
* Set the Large Tube container's Cost to $0.00 and Weight to 3.00;
* Submit to save changes;
* Configure each CD product with a weight of 1.00, to ship in a Large Tube with a capacity of 9999 units.
The above would charge $4 for 1st CD and $1 ea. add'l CD within the US, and $8 for 1st CD and $2 ea. add'l CD going outside the US. You can try applying different figures to get different results, if you wish.
BTW, you might also consider using SwiftCD to duplicate, package and drop-ship your CDs for you, integrated with our cart to have them send CDs for you whenever a payment is completed on an E-junkie cart order:
send order data to them on-the-fly: