https://blog.wongcw.com/2021/03/29/%e7%9f%a5%e4%b9%8e%e7%a0%b4%e7%99%bc%e7%9f%a5%e8%ad%98%e4%bb%98%e8%b2%bb%e5%ae%b9%e6%98%93%e7%9b%88%e5%88%a9%e9%9b%a3%ef%bc%9f/
知乎破發知識付費容易盈利難?