I’ll second what has been said by others about costs on quick travel, etc. being overly punishing for new/poor players, while doing little to those with billions in their accounts. If you really want to combat inflation, then you need to come up with a way to narrow the gap between the richest and the poorest players, and that means that methods that apply evenly, won’t be effective.
Instead, how about a progressive fee for GTN sales and direct trades, i.e. a fee whose percentage of the price increases with the price? You could, for example say that the fee percentage is obtained by counting the number of digits in the price. This would result in a 1,000 credit sale being taxed at 4%, a 1,000,000 credit sale at 7% and a 1 billion credit sale being taxed at 10% (the sudden rate jumps from e.g., 999 to 1,000 credits can be avoided by using Log10(price) to get the rate). There’s also a lot of further options that can be applied to tune the rate progression. If, for example, you’d want to hit the high prices even harder, while leaving low prices mostly untouched, you could get the final rate as 1.5digits. That would elevate a 4-digit price to 5%, whereas the rate for a 10-digit price would be elevated to 57% (this would be excessive in my opinion, but it illustrates that potential for parameter tuning).
After all, the inflation isn't felt at vendors, as those prices are controlled. It's felt on the GTN, so it makes sense to focus measures against it on that.