If you don't mind using Meta services, you may have some luck with big discounts. I've seen BNIB Pixel 9's for as low as $475 on Facebook Marketplace, though most of them are $500-$550. I've purchased my last two Pixels through Marketplace and haven't encountered any issues.
That being said, I like my Pixel 8 Pro and the performance has been great, so I'm not sure the price difference for a brand new Pixel 9 direct from a retailer as opposed to a Pixel 8 is worth it unless you really like the squared off design of the 9.