The valuations are fairly accurate, but the current trend for these is a bit higher than the moderated valuations on the Acaeum.
Can you describe what's going on in the bottom right corner? Is that on the plastic or on the cover? Is it mildew or a stain? Is there any staple rust or interior markings or defects?
If
VG condition, I would guess that this would sell at auction for $450-600.