I had been looking for a used slide to top off an 80% P320 and came across these for $427.71 (normally $549.99):
M17:
https://lanbosarmory.com/index.php?main_page=product_info&cPath=114&products_id=57669M18:
https://lanbosarmory.com/index.php?main_page=product_info&cPath=114&products_id=57769Considering they come with one 17rd and two 21rd mags that are normally ~$40 each that makes the grip and complete slide a little over $300. That's about what used slides seem to be going for
Of course these can't ship to WA because of the mags, but they can ship to a buddy out of state who can separate them
80% P320 frames are hard to come by right now. JSD Supply is fighting the AFT after receiving a cease and desist letter back in May. If you can, go buy a shirt to help support them:
https://jsdsupply.com/shop/jsd-supply-legal-relief-t-shirt/