In today's article about whether a premium membership at Costco or Sam's is worth the extra cost, I listed most of the extra benefits that an individual can receive by ponying up $100. But several fans of Costco have called or wrote to say that paying the extra $50 each year is a "no brainer" because if you don't recoup the extra $50 in your annual rebate, Costco will refund it to you. If you save only $30, for example, Costco will refund you $20 and maybe even $50 if you push it. (Sam's Club has the same policy.)

What is a little confusing is that Costco's Executive members are accumulating rebate dollars toward two separate programs. The first one, available to all members, is through the American Express credit card. Members get a rebate of 1 percent on most purchases, 2 percent for travel, and 3 percent for restaurants and gasoline (for the first $3,000 in gas purchases and 1 percent after that).

Executive members also receive 2 percent back (up to $500) on all purchases made at Costco except on gas, stamps, cigarettes and a few Costco.com purchases. Sam's Club Plus members only get the 2 rebate after spending $10,000 on the Discover card (0.5 to 1.5 percent before that), but it's good on all purchases, not just purchases made at Sam's. The big downside, who takes Discover these days?

I realize that many people don't think they can even save $50 at a warehouse club, let alone $100. Yes, it's true that the larger quantities don't always work well for singles and couples. I, for example, buy the big tub of organic greens occasionally and inevitably I some of it goes bad before I throw it in the composter. Amazingly, the big tub of greens is cheaper at Costco than a small bag at Cub. There's my confession: I'm throwing greens in the composter a few times a year. Take it and run with it, readers who wouldn't be caught dead conspicuously consuming at a Costco or Sam's.

Members, I'll keep you updated on the so-called extra benefits of the $100 membership in the next several months.

BTW, am I wrong about Discover cards? Do a lot of retailers take Discover? I don't own one.