Look at the prices that China is quoting, that is extortion. Anyway, if Pakistanis are happy whom am I to question.
I have looked at the financial aspects of CPEC, and trust me, they are worth it for Pakistan and make financial sense. Investment never comes for free, and the Chinese know that there is a considerable amount of financial risk in CPEC (they're investing at least $46 billion dollars---a huge sum of money). They have included these factors into what they have offered.
And maybe detractors of CPEC like you will one day realize that the very thing that you are criticizing (interest rates of loans / guaranteed rate of return) are among same things that will help ensure its success. The Chinese are not mere bankers for CPEC, but they are the main business partners too.
The more financially incentivized they are to maximize its success, the more successful it will be for Pakistan. In venture capital, if you give low rates of return on invested capital for the investor, they will not devote as many resources as they could have to help it grow as much as possible. They have other, more profitable investments that they will focus on instead. Success in business takes time, effort, shrewd judgement, and lots of hard work. Opportunity cost comes into play. But then again, who am I to tell you? It's all just "extortion", right?
But whatever you may think about the price of investment in CPEC, with all of your financial knowledge, my main point was that you cannot declare that something "is unprofitable" when operations have not even begun yet. Unless you have the power of precognition.