How does a BTER fee imply that users would value their BTS differently? I don't believe you that this is true, and therefore I don't believe that feed scripts should consider this. Perhaps a better explanation is needed?
Sellers obviously get an 1% advantage selling BTS at BTER, and buyers a 1% disadvantage.
So if a seller has the choice to sell at BTER for a price 0.5% lower than on a different exchange they still choose BTER.
The other way around as a buyer I would rather buy at a different exchange with a 0.5% higher price than at BTER with a 1% fee.
As a result there are less buyers and more sellers than on an exchange without this 1% bonus/fee.
Or a different view on things:
Let's assume for simplicity sake that the BTS total supply is exactly 2.50 billion.
Now imagine all 2.5 billion BTS get deposited to BTER. Everybody get's the 1% bonus and suddenly there are 2.525 billion BTER BTS in existance. The market cap didn't change though. (Because BTER didn't spend any money to give out this bonus. They just take it from the withdrawal fee.) That means that the price of BTS and BTER BTS must be different. (Exactly by this 1%)