Ratatosker
Couldn't the author say: 'By buying the first books in my series, you created the impression that you would keep buying them. I kept my part of the silent agreement, I provided you with books, now you're under a moral obligation to buy them.'
No. Which is why authors aren't doing that.
There is a wholly different sort of dependence going on here. I subscribe fully to the idea that GRRM has a moral obligation to finish the series, but not clearly not a legal one. I see you agree with this. By not publishing stand alone books, but rather segments, GRRM is basically providing us with parts of a puzzle, rather than a complete puzzle that you would pay for and be done with it.
So, the only way that you are going to be paying $25,00 for that first set of puzzle pieces is if you believe that the puzzle will eventually be released complete. This makes sense to anyone reading I expect.
Now, to go to your counterargument, as the reader/ puzzle buyer, I depend for 100% on the author providing more books, hence the obvious moral obligation. However the author does not rely to any such extent on me as a reader to complete the series/puzzle. As his popularity increases, as it has with GRRM, my importance to his success has become less than 0,001%. I am irrelevant to the continuation of the series, and GRRM can easily lose me as a reader. Only if everyone reading the series would stop buying future volumes would that be a similar impact for the author. So the moral obligation, if there at all, is on a completely different level.
The comparison would only make sense if GRRM were my personal artist, like Johan Vermeer being commissioned by my good self to do a splendid portrait of me, and I decide to withdraw my financial backing as his patron. Then I too would have a strong moral obligation.
So no, if you're a reader and you don't like the series and choose not to spend more money on it, you are not even morally bound to continue purchasing just to make the author financially independent, since you are just a very tiny and insignificant cog in the great whole. Also, that is simply the risk that the author must take anyway. His series will be a success, or not, depending on many variables. If not enough people buy his books, he will have to find another means of income, because people have a right to log off a series if the author is no longer providing them with what they want to read. But in any case, these people would probably have been far less eager to give him any sort of support if they thought they only ever get half of the puzzle anyway. The very act alone of publishing 1-8th of a story requires a great leap of faith
on the part of the buyer. The buyer takes the risk here, not the creator. In return, the creator has a moral obligation to provide the remaining pieces of the puzzle. If you're looking for anything that is the buyer's counteroffer to the author's moral obligation, that leap of faith is it.