There are really two issues.
First, the GP to $ ratio.
And second, the relative GP value.
First, for the GP ratio.
A) Each token has value relative to eachother. In other words for all tokens there is a ratio of (Token A)/(Token
that is some value regardless of $ or GP. This ratio depends on relative trades. In other words, Gauntlets for an Elixir. Who had to put in more, how much, what were the value of those tokens, etc.
When the GPs (e.g. 1gp, 2gp) themselves are "mapped" if you will, then the value of each of the tokens is computable based on that ratio with the GP. This gives a GP value for each of the tokens.
C) Given a GP value for each token, statistics are used to compute the Average value per toen bag. Based on current values relative to the GP, this total value is 330GP.
D) Each Token bag is sold for $10. Assuming they do not run out and are always available for $10, this gives a ratio of 33GP/$. This means that you can (on average) sell 33GP worth of tokens for $1 and vice versa. Very Rares (on average) make up HALF of the value of each Token Bag. So it wouldn't make sense for a VR to have an average value of $10. You do get other tokens afterall.
While I know that commons are basically worthless to those that have 50+ bags, they still DO in fact have value for the masses.
So having said that, lets look at your ratio and what would happen if that reflected reality.
500GP Emerald for 700GP or $58.
So a person could either buy an Emerald for $58 or 700GP. If the person instead purchased 6 token bags, on average they would get 2000gp worth of tokens (and 6 chances to get the good VRs that are over $10). In other words, they could trade the tokens for GP (basically liquidate), get the emerald and still have 1300GP left over. Or, lets assume the Emerald holder wants items, not GP. The bag-buyer trades his random VRs for say Plate and Gauntlets worth 1000gp, still has 1000gp left over and trades to the Emerald-holder for more than he is asking.
If you make the argument that the bag-holder can't trade his commons, rares, for VRs, then this is the argument to lower their respective values or increase the VR values, NOT to change the ratio. But again, we must all keep in mind that each of us values tokens differently.
In an active economy, assets can be liquidated for their value. Given the GP/$ ratio, if the values of the VRs, Rares, and Commons are captured correctly, then you can determine the UR values in both GP and $ in two ways. By looking at GP valued trades for the URs and by looking at the sale value of the URs.
So, the only basis for a different ratio is changing the values of all of the tokens that are being sold relative to the GP.
Finally, with a ratio of 12 to 1, the AVERAGE Very Rare would be worth like $14. Why would anyone buy the tokens individually? Just by Token Bags, sell the VRs, buy more bags, rinse and repeat.
This is a good discussion though and I am glad you brought up those points.
-Douglas