These are all inter- dependent! If anyone falls out, the entire system will be in jeopardy! So it is impossible to give the entire credit to a single factor behind bitcoin's price.

Scarcity definitely plays a big role in deriving bitcoin's price but the entire thing wouldn't work without a robust network. Also the freedom factor comes into play big time. When the Banking system is showing its weaker side and severe dependency on government, people are more keen to move to a non- controlled environment which gives them a power to control their own funds!

So, many factors come into play in reality!