One issue that has confused some
customers recently is regarding the flat rate shipping additional
charge. The additional charge is incorporated in the original purchase
as well (not just additional items). Here is an example of how you can
set up your shipping properly.
Say you want your additional charge to be $5.00 and you want your original first item to be $10.00.
Instead of having $10.00 in the base cost and $5.00 in the additional cost field you would have...
$5.00
in the base cost and $5.00 in the additional cost field. That way now
when someone buys one product it is $10.00 and every additional is
$5.00 and so on, etc. You just subtract the additional cost from the
total cost and you will get your base cost.