Hi Jackie,
I think the team should just implement a system in which you can buy cartel coins for credits, and base the currency conversion rate on big ticket items being sold, like character slots, renames, or hypercrates.
If a hypercrate is worth 5500 and they sell for 4 billion, it would be about 727,000 credits per cartel coin. If you really want to reduce inflation you'll want to drain the economy and reduce credit rewards significantly to keep inflation from rising back up.
I think taxing these travel costs will only hurt new players and it will do nothing to reduce the amount of credits in the system from the people with billions.