Some have suggested that filament costs are asymptotically approaching a baseline cost - others that costs are linearly decreasing. Does anyone know where to find the trending costs on a single class of filament over the past decade or more?
Part of the reason we are asking is to get enough longitudinal data to begin projecting costs for printing objects in the future. You might think of it like the "Moore's Law" of filament costs.
You could have a look though the various price trackers for Amazon (like ccc and thetractor), for some basic trends. Most of them does not seem to have sufficient data to give any valuable insight, but that could change.
In general, I would refer to the yearly and monthly trend reports found on 3D Hubs. They usually include the average filament order costs per filament type from the previous 30 days, although they do not display it as a continuous graph at this time.