Given the poor trade-in offered by Google Store, it’s likely that Pixel owners wanting to upgrade to the Pixel 8 or 8 Pro are selling their previous Pixel phones to get a better deal. I’ve seen European prices as low as €360 and US prices of $320 for used Pixel 7a phones in very good conditions (there are also lots of Ebay auctions right now that are still under $300).
So for those interested in the previous series, make sure to check out the used market!
I found for example this current auction of a 6 Pro (UK seller) that appears to be in very good condition and hasn’t taken off yet: https://www.ebay.com/itm/256248691768
There are definitely good deals on the older series as people are upgrading to the Pixel 8.