For starters, you have to join in person at one of the 594 stores across the country; you can’t sign up online. And if you do the math you’ll see that the cost of this membership is – duh! – $1 per week, as compared to just 77 cents a week at the regular price.

But Sam’s is betting that the timing of the promotion – when people need all the discounts they can get – will help swell its ranks of members, already 47 million strong. “We’re also trying to bring something positive to people in this troubling economy, says Susan Kohler, senior manager of corporate communications for the Wal-Mart-owned chain.

Well, maybe. But we wondered, given that this is the second weekend in a row that Sam's has run the promotion, whether Sam’s archrival Costco plans to dangle any similar carrot. Sorry, says Richard Galanti, chief financial officer of the 398-store, 40-million-member chain. With business booming and membership renewals at an all-time high (87 percent), Galanti says the company already offers its customers ample bang for their $50 annual membership.

Which chain is better? In years of surveying readers about their shopping experience, Consumer Reports gives Costco the edge (see our latest head-to-head comparison of warehouse superstores). But Sam’s is no slouch either, and it offers a superior warranty for big-ticket electronics gear. So if you’ve got a Sam’s Club near you, and are inclined to try warehouse shopping, this might be the time to leap.