A fix for this is rather simple. The color of a rune should be based on its trader price, not based on its "superior, major, minor" distinction. This way, as soon as something becomes "rare", a downward price pressure due to increased supply should steady the price.
In a similar manner, if there were green, collector, and weapon mod traders, the actual market value of a drop could be determined -- permitting its color to be set appropriately.
This sort of mechanism would make the gold/purple/blue coloring much more informative.
P.S. No, I don't have enough cash to stock up on minor vigor runes... wish I did though
