I am thinking to change the timing belt. The price of timing belt of a genuine Toyota is $38, and of an Amazon is $15. Is there any real difference?

 

Yes.

Not knowing what the Amazon belt is can't state what these differences are..

Spend a few dollars and get the genuine Toyota belt. You might slightly over pay but you will get the best belt.

Another good brand in Bando that makes belts for car makers.

 

Go with Toyota. That is a very critical part.