I haven't tested it myself because I've been a member for a few years now, but I've been told that anyone can get a single day membership for free once a year if you go to the membership counter and ask for it.
Between the quality of their avocado oil (as tested by UC Davis) and the money I save on butter, I can't imagine leaving Costco anytime soon. My partner and I are/were cooks by trade, so we tend to go through an obscene amount of butter, and though the price fluctuates, I'm pretty sure I was paying under $2/lb for standard unsalted butter this last trip. Everything else ends up being a bonus in my eyes.