Chinese e-commerce giant Alibaba began trading on the New York Stock Exchange on Friday, opening at $92.70 with an initial offering price of $68 a share. In the moments after the stock began trading, it climbed higher -- nearly touching $100. But Jim Cramer says investors should beware of buying too high. Cramer says the stock is not a bargain between $90 and $100, and investors who care about valuation will sell it at those levels. The company started trading with a market capitalization of about $228.5 billion, making it more valuable than both Facebook and Amazon. Its market capitalization is still behind that of Apple and Google.