It might simply be a clinical assessment of the raw materials you have used. So that's a simple calculation - canvas plus paint plus framing plus your desired profit margin = selling price.
Or maybe it's the price you put on your own time, compared to what you can sell your skills for elsewhere ?
Perhaps you have an eye on your own immortality and consider the added value you are bringing into the world by your creative endeavours - in which case, that's a valuation that's best left to the ages.
But what if the creative process actually lowers or destroys the perceived value of the source material ?
The most famous instance was probably when Bill Drummond and Jimmy Cauty burned one million pound sterling in 1994. They followed that by touring a short film of the burning and producing a book, while the ashes from the cash went to form a single house brick. You can read more about that here https://en.wikipedia.org/wiki/K_Foundation_Burn_a_Million_Quid.
The story broke on the BBC at the weekend. Click through the links below to read more
"The Paper Boy " was on display at S1 Artspace, Trafalgar Street, Sheffield until July 11th.