What is the ethical way to deal with a mis-ship of cosmetics?

This has happened to me twice. It is a joyous occasion and always a pleasant surprise for the receiver.

The first time, about one year ago, I had ordered a Sigma Paris Palette. I waited 4 weeks to receive it and to no avail it never arrived. When I contacted Sigma they stated it had been lost in transit and sent another one. Lo and behold doesn’t a palette show up four days later, and then a second one two days after that! I decided not to contact them again and keep both palettes. I ended up trading one for a Too Faced Pretty Rebel palette with a user on a multi-user website Reddit under the makeupaddiction subreddit.

The second time was fairly recently. I had ordered a Vice 3 palette from Sephora. The day I received it and gleefully ran to pick it up off my front porch it seemed excessively heavy for one mid sized palette. When I tore it open (hell I was excited I love me those Vice’s) I noticed that there was two. I immediately filled with rage. Stupid Sephora! Why did you send me two?! I didn’t want two! Now I have to march my ass to the store and have them refund me my money for this second palette. Then I ran down the packing slip and it clearly states quantity 1. Well shit. Guess I should shut down my ranty bitch brain for a quick second here. Turns out they really did just ship me two by accident. I took it to the store and they told me to exchange it for whatever I want as long as it was within the same price range.

This is how I came to own my Marc Jacobs The Vamp Palette for $1. Which was the total cost price difference from the two.

There was certainly mixed reaction on the forum that I frequent on Reddit.  What is your take on this? Is it unethical? Dishonest? Or just a stroke of luck if the company doesn’t seem to care?