In my opinion, the price of bitcoin is determined by its supply and demand. But still, there are some factors that affecting the price, example is when the price have reached an ATH and when there is a widespread of FUD.
I am at odds about some of the things that happens with the price of bitcoins, people say that when lot of people buy bitcoins, the price soars and when people start selling it goes down but they forget that as people sell, others are buying as well. I on the other hand think that its the transactions being made and confirmed that drives the price up.