Amazon Prime Day begins at 9 p.m. ET Monday, and Jim Cramer has little doubt that the event will exceed even Wall Street’s grandiose expectations.

“The consensus here is that this makeshift holiday will produce gains of up to 20 percent year over year, new benchmark, which would make it a day that will live forever in brick-and-mortar retail infamy,” the “Mad Money” host said.

Analysts and investors alike see Amazon as a powerful challenger to traditional retail, and the e-commerce giant did not slow its domination ahead of the day’s main event.

Recode reported on Monday that Amazon has quietly been building up an gadget expert service similar to Best Buy’s Geek Squad to help customers with their in-house Amazon devices.

“Best Buy’s the rare retailer that people thought couldn’t be Amazon-ed because the stuff you buy there actually requires help,” Cramer said. “But Amazon’s putting together a unit, we’ve learned, that is set to be able to do exactly what Best Buy does, and pop! There goes the stock of what we thought to be a winner.”

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Amazon’s $13.7 billion bid for Whole Foods has also heightened Wall Street’s concerns about how competitors will fare.

Also on Monday, BMO analysts downgraded shares of Costco to “market perform” despite the company’s better-than-expected sales numbers for June, saying the 6 percent rise in same-store sales would not be enough to compete with Amazon’s foray into groceries.

“Ever since Whole Foods deal, we’ve heard repeatedly that Amazon might buy any brick-and-mortar company that can help them dominate, including the likes of Macy’s,” Cramer said. “That’d be an interesting situation: Amazon knocks down a stock with its own power and then gobbles up the stock underneath when it suits them.”

That said, Cramer reiterated his view that investors should not buy stock in a company just because they think it might be taken over, especially if the fundamentals are weak, so he would not advise buying shares of Macy’s.

The “Mad Money” host was more curious about whether Amazon may be getting too much credit for its widespread destruction.

While some retailers are offering online sales to rival Prime Day, many retailers’ stocks that have declined because of Amazon may have been valued too highly in the first place, Cramer said.

“Take the stock of Costco, which has been hammered relentlessly since the Amazon-Whole Foods tie-up, falling from $180 to $151. Yet even after this stunning decline, Costco’s stock still sells at over 23 times earnings and it has many bulls who remain cheerleaders for the company,” Cramer said.

Cramer sees some value in the stock of Macy’s, which trades at just under 8 times earnings but yields a hefty 7.2 percent. The company makes money and owns a lot of real estate, but it has $15 billion in debt, which is a red flag for shareholders.

“I say do this: let the retail stocks come down for another couple of days,” Cramer said. “Let Amazon blow out the numbers for Prime Day. Let everybody cut estimates for all the others. But remember: Not all retailers are created equal. Some are indeed better than others. Not all can be Amazon-ed as easily as you think, while the stocks of others reflect a brutal Amazon-ing that may never occur.”

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