Hypothetical question
 

The air fare rule states that if you decide to change your ticket, you would have to pay a $64 cancellation fee plus the difference. But what if the new ticket is significantly cheaper? Does the airline pay you the difference, too?
Say you're replacing your $400 ticket with one that costs $200.

If you deduct the $64 change penalty, the airline still owes you $134.
In your experience, do they pay you the difference?

Yes. But also ... quite hypothetical.

Some airlines will, instead, give you a voucher that you can apply against cost of future travel (usually valid for 1 year from the date you are re-ticketed).

This has happened to be with Alitalia and I ended up paying the cancellation fee-got nothing in return even though the second ticket was cheaper.

AliceWilliams, the same thing happened to me. I booked a much cheaper ticket through Czech Airlines. I paid the cancellation fee but got nothing in return. One would think that they would at least substract the difference from the cancellation fee. I guess that puts our hypothesis to rest.