A standard Sam's Club membership is $50 a year. You'd recoup that with a single SWA gift card; the $500 cards normally sell for $450. During the sales (seems like they've been doing the sales two or three times a year the last few years) they sell for $430. I'd say it's well worth the membership fee if you buy a lot of the SWA cards. I'd say it's almost worth it even if you only buy two or three of the discounted cards in a year.

Also, you don't have to be anywhere near a Sam's Club if you're only joining for the SWA cards. The discounted cards are always available over the Sam's web site, including during the $430 sales. In fact, my local club rarely has the $500 cards in stock; every one I've ever bought has been electronic, through the web site. You don't even need to wait for a physical card to be mailed. Buying them over the web site is all electronic, you get an email with the card numbers and just enter them into the SWA web site to use them when you book a flight.

A Costco membership is $65 a year. I'm not a member, but I know they also sell the cards online like Sam's Club. You can see the discounted $500 for $430 card on their site right now, even without logging in as a member.

A BJ's Warehouse membership is $55 a year. Again, I'm not a member, but I know they sell the discounted $500 cards. Their regular price isn't discounted as much as Sam's and Costco, though; the normal price for a $500 card is $484 through the web site.