Of the last six consignments I sold, two were rare Golden Age romance books, three were original art pieces, and one was a rare TMNT comic signed and sketched by Eastman & Laird, so GPA doesn't apply. I tend to buy and stuff like that instead of the normal superhero carp with lots of sales history. Maybe I left money on the table but when there's no comparables to establish baseline prices that's not really knowable.
In the event that I did send in GPA heavy stuff I would price above recent sales and take offers. For particularly hot books I would price aggressively.