The discount IS the price for new customers. Verizon offers phones at two prices, full retail (which you can purchase at any time), and subsidized, which you can purchase at any time you are eligible to sign a 2 year contract. Since one or more of your lines is eligible to sign a new contract, you can pay the subsidized price for a new phone.
Thank you for your reply, spottedcatfish.
spottedcatfish is correct. When you are eligible for an upgrade it means you are able to receive a device at a discounted price with a new 2 year agreement. Please feel free to browse through our current devices. You can conveniently compare up to five at a time to help you decide which device is best for you. Keep in mind you can always upgrade directly from My Verizon.