Furthermore, they offer a full guarantee. Don't like it and they will refund you.
How about I rephrase: "I felt lied to and taken advantage of, and I decided not to bother being a customer any longer, given that I shopped there very infrequently and despise high pressure sales tactics."
In the end, this is about my personal customer experience, which I've subjectively decided sucked enough to outweigh the utility I got from Costco membership. I can't stand pushy salespeople, and I basically argued with the cashier for several minutes telling him that I didn't want to upgrade. I said no at least five or six times.
I should have just stuck to my position, but after I was told that there was literally no way to lose money even if I never took any action to get a refund, I caved because I wanted to go home.