As a quick recap, Google's Pixel 3 and Pixel 3 XL smartphones come equipped with Qualcomm's Snapdragon 845 SoC that has eight CPU cores and an Adreno 630 graphics processor. These smartphones also have 4GB of RAM and they come with either 64GB or 128GB of storage. The phones differ in size with the Pixel 3 XL being somewhat larger. The Pixel 3 has a 5.5" 1080p display, and the XL model has a larger 6.3" display with a resolution of 2960x1440.
The discount system setup by Google is a little complicated. You aren't required to purchase two identical phones to take advantage of the promotion, any combination of Pixel 3 or Pixel 3 XL phones will work regardless of their storage capacity.
To obtain the largest discount available of $450, you will need to purchase either two 64GB Pixel 3 XL or two 128GB Pixel 3 XL smartphones. You can also purchase one of each of these and obtain the full $450 discount. Discounts for other smartphone combinations range from $350 to $400. Whatever combination you decide to go with, you're getting at least $350 off the total purchase price.
Google is offering this promotion as part of its Valentine's Day celebration, and it will continue to offer this deal until February 25, 2019.