I am suprised that you completed the order without doing your research first.
If someone came into my Coffee House. Had an espresso and a fresh baked scone.
Then returned half an hour later. Saying that a similar product was cheaper down the road. Could he have his money back, including the waitresses wages.
I should have gone into what my staff call "John Cleese Mode"
I think they have been very fair to you in accepting a straight loss with such good grace.