Found this deal via an ad that popped up.
Seems you don't need to own any of the phones to get the 20% off.
Some reports if it working on the pixel 4a too.
I did not go through all the options, but
$999 to $799.20 for pixel 5
$799 to $639.20 for a pixel 4a with 5g.
$599 to $479.20 for a pixel 4a
Mod Note: You need to obtain a unique code from the linked page (select any phone), but you don't actually need to trade it in. The code you receive will apply to all 3 phones, even the regular pixel 4a, even though it's not a listed option on the linked page.