sarcasm where sarcasm is not due

Over dinner the family was discussing budget cuts we could make ('tis the season to cut back on discretionary spending; we are attempting to figure out whether we can afford to send Iris to private high school).  The Sober Husband noted that he rarely drives his car nowadays, since he normally takes a luxurious company bus to work (the bus in question has hardwood floors, a very friendly driver, and a WiFi connection faster and more reliable than any home internet we've ever had).  

"I wasn't asking you to sell your car because I know you love it so much," I said.  The Sober Husband and his Prius (nicknamed by me "the Science Coffin") seem like a perfect match.

The Sober Husband scoffed. "I don't care if that car lives or dies."

I looked at him in horror.  "Don't talk that way!"

Iris intervened.  "It's not like it's the Baby," she said, referring to my beloved MINI Cooper.  "The Baby is a beloved member of the family.  His car is just a car."

"I'm so glad you understand," I said.

Iris rolled her eyes. "I was being sarcastic."