Well, having seen some of that world from another perspective (writing, not photography), it seems to me to be almost like an inverse triangle where the artist/author/photographer puts in the graft, supplies the materials (time, research, equipment, physical photographs, or a painting, or a book in written form, something in writing), creates - or crafts - the work in question, and that this whole secondary industry (galleries, publishing companies, shops, outlets) lives off the proceeds of these works, creaming increasing profits as the chain progresses from artist/author/photographer to the vendor of said product.
This is because - usually - artists or authors - are not really constitutionally capable of marketing or selling their own work, or putting a true value on it, or making their way in the world of trading or the market. They can create, but the world of buying and selling in the market is alien to them - indeed, some artists disdain it.
Now, I am an historian by training and background, and used to be an academic before being enticed out from the Groves of Academe into The Real World.
Anyway, some years ago, a book - a history book - I wrote was published, received excellent reviews, was put up for some prizes, and proceeded to sell very well. (That is, it sold a few thousand copies, which in the publishing world of history books is very good indeed).
Candidly, to some extent, I was still at the stage described by
@kenoh - astonished and delighted and awestruck that people were actually prepared to buy what I wrote, and that a publisher was prepared to put serious resources into making a beautiful edition (and it was a beautiful edition) out of my book.
Anyway, I remember reading the financial statement the publishers sent to me with stupefaction, as I had been thrilled to make a bit of decent money - and I did - briefly - make some decent money - in the year immediately after it was published.
However, if memory serves, I received 6% of each paperback sold, and 12% of each hardback. Everybody else, from publisher, to vendor, made an awful lot more. Researching, and writing that book took years of my life, - which I loved as an intellectual exercise - but I do vividly remember how stunned I was to realise that everybody else in the process (that inverted isosceles triangle again) made an awful lot more than I did, out of what was, in essence, my intellectual labours.
But that seemed to be the price that I was expected to pay for having been published. And - I suspect - that their argument would have been something along the lines of that most history books do not even recoup the cost of publishing them in the first place in subsequent sales. They will further argue, that therefore, they, as publishers, have to make a living as publishers of books that need to be - and deserve to be - published - even though they fail to sell well - because profit is not their sole motivation - which means, in effect, that the books that sell well serve to subsidise the others.
