I had some system, which may or may not be something like this, but this is what I'd use:
Assign a value to *me* for each uncommon or rare. That will likely involve mulching some of the tokens so means how much I would buy trade goods for, which might be $0 for something like DP due to getting enough through other ways. Total for a complete set. Divide by 40 to get average uncommon or rare value. Multiply by 240 or 120.
Note that this will change based on availability of singles, changes in trade good needs/valuations, etc. So, it's pretty tedious.
While forumites should be able to get single rares insanely cheap, I doubt they do. It's too much effort for people like me who have more rares and uncommons than they know what to do with to list them. I'd happily give away various stuff to people who would value it or sell for nominal amounts, like $1 for good rares, but it's too much effort. Putting something like "Have rares you might want for $1." in trade thread is also too much work on a buyer's part to chase when can go to one of the stores or do something like hunt for a bag of rares, as rare as those are.
Too much effort because the audience is wrong. The people who don't use the forums who give Gaming Etc. or whoever several bucks or $5 or $10 or whatever it is that I've never done are the audience that would love this stuff. Lot of us on the forums don't have use for hardly any uncommons or rares or will just get them in treasure, anyway. I wanted a rare bag from a few years ago, couldn't find one for a reasonable price, got everything I wanted through treasure, anyway. Meanwhile, not having to deal with sorting, storing (weight is a big deal with TD), transporting/shipping, packaging a bunch of stuff I don't want is preferable.