If you mean literally writing the check then yes you paid it. But then you paid both halves since you also wrote the payroll check. That’s fine, you wrote the checks and paid all of the Social Security taxes. So I suppose your employees should get nothing.
Must be nice to have an employer who does not require you to earn 7% of your benefit package. I supppse you “gave” them healthcare insurance as well. And when it was time to cost out your product you didnt include any of the stuff you gave them in the labor component.
You will be ok once you get out in the real world and find out first hand how things work. In the meantime, stick with the theories you were taught in school.