Is it not cost-effective for the second-level construction engineer to pay social security and not to pay the affiliated fee?

Not cost-effective. Paying social security without paying the affiliated fee means that the salary is mainly composed of social security, and the social security fee is not high, which leads to low economic income and is difficult to meet daily life and personal needs. Paying social security without paying the affiliate fee means that you can enjoy other benefits, such as year-end bonus and holiday benefits, which makes the overall treatment worse than other employment methods.