In addition to offering the device with a discount, Motorola allows you to customize your phone at no extra cost using Moto Maker. This free customization excludes the Bamboo back cover as it costs an extra $25.
The Moto G4 Plus has not been included in this offer. If you would like to get the Moto G4 with the discounted price, you can check out Motorola's website or Amazon; where it is also offered at the same price. Amazon, however, does not include free Moto Maker customization.
Source: Motorola, PhoneArena