Unlike explicit costs (like tuition and fees), this is an opportunity cost that isn't directly paid out but represents the value of what you give up by choosing to go to school instead of working. This could include:
* Salary earned: The money you could have made in a job.
* Job experience: The skills and professional network you could have developed.
* Potential promotions: The career advancement opportunities you might have missed.
Essentially, it's the value of the next best alternative you gave up by choosing technical school.