Funny thread. I've seen a couple of funny things in this regard. One time, when I visited a local store, I overheard an elderly gentleman talking with the store owner about making a fake invoice for the purchase. I proceeded past the pair into a listening room where an elderly woman was listening to the music. We struck up a conversation and she informed me that, at this moment, her husband was trying to get a fake invoice that he planned to present to her. She said that explained that her husband feels guilty about buying expensive gear so she plays dumb because he worked so hard all his life and she wants him to indulge in his hobby.
I know another couple whose husband has a top end Naim system. What he particularly likes about the Naim gear is that from bottom to top of the line, the stuff looks the same. As he "replaced" gear moving up the line, his wife would have no idea as long as he moved into the system when she was not at home.