Rick,
Not all of the values have changed. Seems like many of the low end trays have stayed low end...especially the "hockey puck" stackers and the flared style trays.

The best reference available (and it's AWESOME!) is Mark Englebretson's ashtray site. He has an amazing collection, and he's gotten scans & photos from all of the top ashtray collectors, and the "little guys" too.