I really doubt charms would ever be as expensive as you guys imagine, at the moment of course everyone would pay an 'exceptional' price because they can't buy them, but I bet if from day 1 they had been tradeable that their price would be much lower.
I would pay any money for golds/greens at all, they're shit for training and .
Crims I might pay 500gp per, and Blues maybe 3-5x that.