Ace said:
As an example Mythic Polynesia s untouched but its a lot of work for a very little gain. I doubt it would sell 100 copies. There is no way I am going to write and edit 128 pages on a topic (a couple of months work) and than maybe sell 50 copies when I could write 14 Spetums in a weekend and make almost as much
If I may be so bold, I think you pose both the problem and the solution.
Don't write a single, 128 page book on Mythic Polynesia. Write a 14 pager on how the warrior classes would fit in the setting. Then write 14 on the divine casters. Then the arcane casters. Then 14 or 28 on the monsters. Then write a couple of adventures. At the end of it all, combine them into one big book and sell it as a collection and individually.
Eventually, you end up writing all the same content as your 128 page book. You still get the same end result. However, your sales may actually be higher. People looking for new wizard options may buy just that one at the lower price. People looking for new monsters may do the same. You might have only gotten 50 purchases for a 128 page, $12 pdf (total $600). Instead, if you can get 20 people to buy each of 14 smaller supplements at $3 (total $840) you may end up in better shape overall.
Further, your original products are making you money while you finish up the later ones. That way, you don't have to wait until all 128 pages are done before you get your first buck.
I don't think it's any industry secret that there are already people doing this. Take a look at Louis Porter Jr.'s
Mutants and Masterminds stuff or some of the Ronin Arts pdfs over on RPGnow. Most are available both individually and then later as collections.