I'm doing the edits for a novel under another pen name right now. In addition, I have yet another name and career, as a visual artist. That career is taking an interesting turn: I'm opening a eBay store. Up until now my sales were all commissioned work (wedding portraits, mostly). Ebay has less certainty than commissions, because I paint first and sell next. Portraits, I sell first and paint later. It's a different kind of stress.
With portraits, I am always worried that the client will look at the final product with that expression you sometimes see on Trading Spaces. The couple comes home to their new living room, which has been painted pepto bismo pink with hay glued to the walls, and they have this expression that says, "Oh god, this is so aweful it deserves to be burned, but I don't dare say so out loud because I'm on television."
With an eBay auction, the buyer has already seen the work, so presumably they like it. You just have the misery of waiting out the seven day auction to see if anyone likes it or not.
Even this, however, is instant gratification compared to writing. First of all, it takes quite a while to write a novel, much longer than it does to paint even a fairly large painting. During November, I was trying to do both, so this point was driven home to me! But let us suppose that one does take a whole month, eight or ten hours a day, to paint a piece. One can still turn around and sell it (or not) immediately. The client pays, and the starving artist can finally make that much overdue trip to the market for more ramen noodle.
For comparison, what happens when a writer finishes a novel or a short story? The writer sends in the piece to a likely publisher. Two or more months later, the publisher expresses an interest. Some more correspondence may then, at last, lead to a sale.
But that's not the end of it. The writer may recieve an advance for the novel, in which case, hallaluyah, the writer can buy some ramen noodle for her long suffering husband. However, the novel or story is still far from published. It must be bounced back and forth, through the galleys and whatnot, and this takes several more months. Then it is set up for print, again, more months.
And when it finally comes out in print, the thing has to sell itself all over again, this time to the consumer.
I think that's the crux. A writer must sell her work twice, first to the publisher, then to the reader.