Well, knowledge cannot be quantified in that way. There are different ways of learning nowadays and teachers are always required to know things in a better way. Knowledge always increases with sharing and while knowing different things there will be doubts.
Teachers doesn't always mean a school teacher or a teacher of some higher institutes, anybody can be the teacher if she/he knows things better than you. You can learn from anybody. The most important part here is, we do not learn from books or searching through internet only, we learn from following others also and that is the most important aspect of a teacher.
When a child starts learning she/he doesn't know anything about alphabets or internet, it is the parents from whom the child starts learning. After a certain stage when the urge of knowing things is developed, the child looks for different means to gain knowledge. So, teachers are always important than any other means of learning because it is the teacher who helps us to develop the urge to know more.
"Life is easier when you enjoy what you do"