I think the issue here is the structure of the contract Moore & Gibbons signed when they produced Watchmen...
Initially, M & G were told that they would retain the intellectual property rights to the characters they created for Watchmen as they were the adaptations/extrapolations of the Carlton Comics characters (Dr Manhattan was Captain Atom, Rorshach is The Question, etc, etc) then owned by DC.
Once they had finished, DC started talking about doing a second series without M & G - Moore pointed out that they were "their" characters and so DC couldn't do that without M & G's permission. DC then reneged on the IP part of the contract, saying that because they were analogous to the Carlton Characters, they owned them.
At this point, DC had done a similar thing with the name Captain Marvel when Marvel used it, resulting in the renaming of the Marvel character as Mar-Vell.
However, a legal battle ensued when M & G weren't paid according to the contract - they were paid on a flat fee basis with a percentage of all future royalties from subsequent reprints of the series. When the TPB version came out, DC never ponied up the cash, resulting in the lawsuit that was settled out of court.
I also think that there's a common misconception amongst the general public that comic book writers & artists get paid huge sums for their work. The big two only offer flat rate deals these days that work out to be based on overall projected sales of the books they are working on & companies like Image & Top Cow offer 3/4 cents per issue sold to writers & artists.
When you consider that the best selling comic last quarter was X-Force with only 250,000 sales worldwide, that's not alot of money. Then when you look at the independent companies, IDW's The Transformers only sells about 25,000 copies a month, you're looking at around $750.00 per issue for the writer & the artist each...hence the reason virtually every book these days outside of the Big two are looking to be optioned as films...
And we all saw the abortion that was Wanted! Well, actually, I didn't on principle...