After shares of burger chain Shake Shack opened at $47 on Friday, more than double its initial public offering price of $21 a share, Jim Cramer says the bar has been set too high. Cramer says he finds the price worrisome as he's concerned people will forget about the company next week as excitement over the IPO fades. He reveals what investors who got in on the deal should do with the stock and tells those who missed out, not to fear. Cramer advises those who didn't get shares to wait, as he believes there will be a better price. As far as the company itself, Cramer calls it an amazing business that makes a ton of money per store. He says he believes in founder Danny Meyer, although he believes the stock's high price puts pressure on him, and investors should wait for it to come down.