Shares of Costco Wholesale (NASDAQ:COST) saw a 5% bump last week, after the release of third-quarter results. Key fundamentals came in higher than expected -- no doubt a big reason for the rise in share price -- but comparable-store sales were uncharacteristically flat.

In this clip from the Motley Fool Money radio show, Chris Hill, Matt Argersinger, Ron Gross, and Jeff Fischer talk about why the comps weren't as good as the pop might imply, when investors might want to start getting concerned about the company, and how successful the store has been at boosting its e-commerce sales.

A transcript follows the video.

This podcast was recorded on May 27, 2016. 

Chris Hill: Shares of Costco up this week, after third-quarter profits came in higher than expected. But for the first time in six years, Matty, same-store sales were flat.

Matt Argersinger: Right. I was trying to figure out what investors actually liked about this report. Comps were flat. If you strip out foreign currency, gas sales, OK, up 3%. But overall revenue up just 2.5%, really only because they're opening new stores. Profit's up 6%, a little better than expected. But these aren't exactly the growth numbers that, in my view, justify a P/E of 30. 

Jeff Fischer: Such a hater.

Argersinger: I know. My only guess is that the traditional retail industry has been so bad over the last six to nine months that Costco's slightly better-than-expected results is getting it some love.

Ron Gross: Did they talk about retention at all? Are they seeing any slippage there?

Argersinger: There's no slippage of retention. I'll point out that they had better-than-expected membership fee growth, which, of course, is a pillar of the business. So that's probably giving it a little bit of a boost.

Hill: Six years of same-store sales growth, that's phenomenal, and that was bound to end at some point. I think the question, Ron, becomes, three months from now, if we're looking at this same number again, then it's no longer a speed bump. Then it's actually a point of concern.

Gross: I think that's fair. But as Matty pointed out, I don't really think it's as bad as it looks because of foreign currency and because of gasoline. I think the numbers are still pretty solid -- perhaps not as robust as they used to be, but they're still opening new stores, they're growing on a per-store basis, retention is still good, you still have the model working. And I'll add that you're probably ripe for another rise to the membership fee at some point, which is another lever they can pull, assuming the economy and the member base are strong enough, so we can see some growth there.

Argersinger: There's also been a shift now moving to the new credit card, which, we'll see. That could either be a good thing and lead to a lot of growth membership, or it could not. We'll have to see.

Fischer: I have a question for you two guys, who I know follow Costco closely. Does management talk about [] (NASDAQ:AMZN) much at all in conference calls?

Hill: Would you, if you were Costco? [laughs] No!

Argersinger: Costco doesn't really mention Amazon by name. But they talk a lot about their own e-commerce efforts, which are, on a relative basis, doing quite well. And they have, of course, a relationship with Boxed, which is working out.

Gross: You can -- as you can with Amazon, not to this extent -- buy a lot of junk, an amazing assortment, you can buy online as well. I've bought some interesting things myself.

Fischer: I would just think, over time, Amazon will eat into that. Even Costco's business is vulnerable with subscribe-and-save on Amazon and all the Prime members.

Argersinger: Pantry deals, that kind of thing.

Fischer: Exactly. We're buying more and more of those basics from Amazon themselves.

Gross: But in, like, a Best Buy, where we say Best Buy is really just a showroom for Amazon, I don't think you'll ever say that about Costco. You're going to Costco, you're leaving with a cart full of stuff. If you're going to make that effort --

Fischer: If you're Ron.

Gross: [laughs] I don't think you're going to see, say, seven dozen pieces of licorice and say, "I'm going to go buy it on Amazon." You're going to walk out with it.

Fischer: Yeah, but they could just not go to Costco, period.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.