The value is also based the difficulty to obtain (mine) it
This is a common mistake. Its value
isn't based on the difficulty. Its difficulty
is based on its value. Think about it, if there is more demand and the price rises, the difficulty rises too, because mining becomes more profitable. If there is less demand and the price falls, the difficulty does too.
I see it as a circle. Price feeds greed i.e. investment hence increase of difficulty, difficulty means network security which ends up asking for better price.
I am also not convinced that a "crypto winter" decreases the difficulty accordingly (in percents).