LadyTramp,
Why don't you just ask them at the check out to quit asking you ever again? Maybe there is a way they can flag the account so they won't bug you? I'd ask.
...so they wrote the word NO in black permanent marker on my card. If they approach me with their scanner, I just show them the no and they say okay. Ask next time if that's a possibility or just do it yourself.
The employees have to have some incentive to do this.
The memberships are how Costco makes their money, period.
I feel a little left out LOL! We shop there a lot and never once have been asking about upgrading to the executive membership. When we bought our furniture years ago, and didn't know about it, I wish someone had! We could have made some money on the %.
Memberships are a tiny fraction of Costco's business model.
. I had enough so I told them I would flip a coin to settle it. Heads I would upgrade and tails I wouldn't. They couldn't believe I would leave it to chance.
I flipped a coin and it came up heads, so we upgraded. They were high-fiving each other and other employees. It is hard for me to believe they don't get some kind of bonus or something of value. We got a check that year for $125.
We moved last year and I downgraded as we don't have a Costco in town any more. We don't go very often (one hour drive) and therefore we don't spend much so they leave us alone about upgrading now.

Sam's Club is doing the same thing. I'm sure they get a kick back from selling them, so they are pushy.
Sorry, but simply not true. Memberships are how they make their money...I get my share holder and employee reports that clearly show that over 70% of Costco's revenue/profit is generated soley from memberships.