This has been a common question. An example would be trying to get TWO (2) of the Perfect Pair.
Please take the cost of one: $79 + shipping (if applicable) and add another $79. Don't worry about extra shipping costs! So to make it a little more clear:
Perfect Pair - $79 + $15 (int'l shipping) + $79 (extra Perfect Pair) = $173
Only one shipping fee, the additional shipping fee will be waived for you!