I remembered this image, and couldn’t find it, but I finally found it again:
Here’s the source: Best "GoTo" Filament - #15 by user_482380812
Not sure what those round containers are, but they look a lot like the printdry containers:
at about $12.50 each, or roughly 3x a cereal container. They do stack rather nicely though, and perhaps (?) they have a better seal. Not sure.
At some point I’m going to test various containers for moisture leakage. Extremely preliminary measurements on the cereal containers are: about 0.1g moisture intrusion per day. Not sure if that’s through the seal or the plastic itself. The plastic may seem improbable, but it has a much larger surface area, so I wouldn’t rule it out. I’ll probably try a stainless steel container with a silicon gasket and see how that compares. It would be a big win if a simple cookie tin could do the job, as those are super cheap. They seem to keep Danish sugar cookies dry, so why not filament? Maybe $1/each, or “free” with cookies. Worst case: seal it with non-China metal HVAC tape that meets a NIOSH standard for ductwork, and you’re probably guaranteed to come out ahead. Still… I’ll wait for the data, and then we’ll know for sure. 
One of my favorite quotes from “The Imitation Game”:
The Americans, the Russians, the French, the Germans, everyone thinks Enigma is unbreakable. Alan Turing : Good. Let me try and we 'll know for sure , won’t we?
I’m no Alan Turing, but… I like the idea that you don’t know until you devise an experiment to decide the matter definitively. I wish more people would do that. It would spread the workload considerably!