It looks like a good idea for profitable writing. However, I believe that successful "$500" stories are not only about the "what" but also about the "how.” Maybe they are a lot more about the "how" rather than the "what.”

The appeal of a story is a combination of many things, and its topic is only one of them, I think.

With this in mind, I must say that your writing is outstanding, Harold, and you know that. Therefore the "winning" topics work well for you, but might not work nearly as well for others :-)