What does the Balloon Price refer to in mailing services?

The Balloon Price in mailing services specifically refers to a pricing strategy used for parcels that are lightweight but take up a larger volume in shipping space. It does apply to Priority Mail addresses, particularly those for delivery to specific zones, which are typically designated as zones 1-4. This pricing method is utilized primarily to ensure that shippers who send lightweight yet bulky items do not incur excessively high shipping costs. The Balloon Price helps both the service provider and the sender manage costs while still maintaining affordability for certain types of deliveries.

The other options refer to different aspects of mailing services. For instance, pricing for heavier parcels, discount rates for bulk mailing, and extra fees for international shipments are separate pricing structures and do not relate to the definition and application of Balloon Pricing. Thus, understanding that Balloon Price is specifically tied to the volume pricing for lightweight parcels directed within certain zones clarifies why the indicated choice is correct.