这是因为在双写最后一个辅音字母的同时，去掉“y”，用“-ier”代替。
因此，“cheap”的比较级是“cheaper”。
这样的规则是为了保持词义的一致性和发音的规律性，以便更好地理解和使用英语语言。
在写作或口语中，正确使用这样的比较级形式可以使句子更准确、流畅。
所以，当我们要表达“cheap”的比较级时，不需要双写“p”。
When an adjective ends in a consonant letter plus "y," the comparative form of the adjective ends in "-ier." This is because we double the final consonant and replace the "y" with "-ier." Therefore, the comparative form of "cheap" is "cheaper." This rule is in place to maintain consistency in meaning and regularity in pronunciation for better understanding and usage of the English language. Using the correct comparative form like this in writing or speech allows for more precise and fluent sentences. Hence, when expressing the comparative form of "cheap," there is no need to double the "p."