Lets compare to the mint: When you buy from the mint with the intent of depositing it right in the bank, your are going against their clear rules prohibiting that, costing them a percentage for the CC processing fee, and costing them hefty shipping charges.
Compare to buying something from a store with the intent of returning it: You are costing them at minimum that they will not be able to resale it at retail value because it was used.
Now when you buy a refundable airline ticket especially for a ticket six months in advance, they technically lose nothing from you (and even get to keep your money fee free until you return it).
This would seem way more ethical then the above options.