According to the numbers Motley Fool Inside Value selection Wal-Mart (NYSE:WMT) released this morning, its June same-store sales rose 1.2%. That wasn't a huge surprise; the company had projected June growth between 1% and 3% when it released its May numbers last month. However, the text describing its performance was a lot more intriguing.

Wal-Mart continues to see less traffic in its stores and fewer trips by its customers, but the company is making up the difference with higher sales per ticket. As I interpret this, some consumers are feeling the pinch from $3-a-gallon gas and rearranging shopping trips accordingly. While Wal-Mart is faring reasonably well so far, this isn't a friendly trend, since retailers in general are aided by more frequent visits, not less.

Looking a bit deeper, Wal-Mart's Sam's Club wholesale warehouse business turned in a 1.3% same-store sales increase, and the U.S. Wal-Mart business turned in a 1.1% increase. In comparison, warehouse-club competitors Costco (NASDAQ:COST) and BJ's Wholesale Club (NYSE:BJ) turned in a 6% increase and 0.1% decrease, respectively. Same-store sales at rival discounter Target (NYSE:TGT) increased 4.8%.

Looking at the raw numbers, it appears that Costco and Target are outperforming the rest of the pack. But one month's worth of data doesn't make a trend, and there's more to the profitability of a business than same-store sales. As a Costco shareholder, I can honestly say that I've thought long and hard about buying Wal-Mart shares at prices around $45. The longer they stay in this vicinity, the more intriguing they become.

In short, I don't think investors should underestimate Wal-Mart. The company is attractively valued, and the business's overall performance in the last few years is much more impressive than that of its shares.

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At the time of publication, Nathan Parmelee owned shares in Costco, a Motley Fool Stock Advisor pick, but held no financial position in any of the other companies mentioned. The Motley Fool has an ironclad disclosure policy .