What is the difference between cheaper oil paints and more expensive ones? I use Winton oil paint that I get for £8 for a 200ml tube (for any colour). Some tubes from other ranges (from the same shop) cost up to £160 for a tube the same size - and there is different pricing for different colours. There are several different ranges in between at different prices.

Why the huge disparity in pricing for paint, and what do you get in the more expensive ranges that you don't in the cheap stuff?
There are many things that can set apart great paints from others:


working-qualities of the oil 
specific source of the oil 
chemical pigments 
pure-mineral pigments 
colorfastness of the pigments 
metals in the pigment 
consistency of pigment grain-size 
pigment density / fillers.


Each of these can mean different things to the rest of the materials you will use in producing your painting, which is a bit beyond the scope of this question.