If you are buying an item for someone else's wish list then you pay for it.
If someone buys something and sends it to you, they pay the cost of the item and shipping. If you live outside of the USA then there is a chance you will have to pay something, IF the order gets stopped by customs and your country wants you to pay import taxes.
To send an item to someone, put items in your shopping cart as normal but do not check out. Instead visit the member's profile wishlist page. From that page you can send your order to them by clicking the 'Send these items to XXXXX' button.