At the end of the email for ride photos, it has the following, along with a unique promo code. At Google Store check out page, the code takes $150 off making it free.
The ride was across the street from Las Vegas Convention Center, inside the Google building. After the ride, if you scan your badge at the booth with ideally your picture, you'll get an email for the pictures, and the code.
below is copied from the email.
"And guess what? We'd like you to experience hands-free help at a glance in your home with a Google Home Hub — on us!
On Google Store, add a Google Home Hub [google.com]
to your cart, and use this unique, one time code at checkout to get it on us, shipping included*. Enjoy!"