Prices are based on sales data or actual copies selling in the marketplace.
If there is, or has been, greater demand by collectors for later editions of a module (either because it is rarer and harder to purchase, or because there were fewer surviving copies due to lower printruns, or even poor quality resulting in quicker degradation) then the prices paid by collectors for the surviving copies coming to market reflect that.
The estimated prices on Acaeum are purely a guide extrapolated from real world sales.
A member of the valuation board may be able to provide a specific insight into
PotVQ specifically.
This week I've been mostly eating . . . The white ones with the little red flecks in them.