While dressing formally on your low professor's salary isn't easy, it's worth it. It helps you convey a sense of authority and gives students more confidence in your teaching.
At least, that's the theory. It's also possible that students will see you as out-of-touch and give you low scores on RateMyProf.com.
You can't fully control how students rate you, and it can be enjoyable to wear formal clothes. That's why you chose:
As you walk down the hall to your class, you straighten your jacket, enjoying how it hangs on you. You're ready.
The classroom's empty when you arrive, just as you planned. Warm late-morning light falls from the windows and onto the student tables. You have time to deposit your notes on the desk near the front of the classroom, check that the dry-erase markers actually mark, and walk past the student tables to the back to get the feel of the room.
The students begin trickling in. You smile and, roster in hand, talk with the students.