Unless it's meat-cooked-in-milk, it's fine. And let's assume you bought the non-kosher stuff by mistake.
The primary source cited by that article is the Gemara Pesachim, 23a:
תנן ציידי חיה ועופות ודגים שנזדמנו להם מינין טמאין מותרין למוכרן לנכרים שאני התם דאמר קרא לכם שלכם יהא אי הכי אפי' לכתחלה נמי שאני הכא
We teach: trappers of wild animals, birds, and fish who happen upon a non-kosher species [in their traps], are allowed to sell them to non-Jews. This is permissible because the verse reads of yours. If so, could one plan to sell non-kosher species as a business? No, that's different as the verse says ...
So if I intended to buy the kosher vegetarian can of soup, and mistakenly bought a non-kosher one that contains pork (let's assume it doesn't also contain milk), that's entirely analogous to our hunter who only wound up with non-kosher by mistake: he may absolutely get his money's worth out of it through a non-Jew.