Originally Posted by bennos

I'm going to vote "moderately shady". DL advertises a flight with availability at 25k or $330. It's completely unintuitive to the average person that purchasing with miles would cause the cash price to change, or vice versa, and in fact the implementation is explicitly designed to make it difficult if not impossible to do. eg: A customer friendly implementation would allow you to book both tickets at once.

Sure, you're still within the fee free cancellation period (restrictions apply, especially if re-using an existing ticket), but it's still effectively false advertising.

For another example, if I go to a store and want to buy two identical shirts, one using cash and the other using a gift card, the price of the shirts doesn't change while I'm switching methods of payment simply because "inventory decreased". A price was advertised, I agreed to the price, and I went to pay. Only in the airline industry do we get BS disclaimers like "The advertised price is not an offer and is subject to change" (the fine print on every Delta purchase). Barely legal perhaps, but completely unethical.