That is more understandable, Deecey. :) A niche item, especially here, is almost doomed. I don't expect my mermaid character to sell very much because of the lack of that particular type of character use in the galleries. She's a niche but unique. Same with anything for Koshini and gang. And then there's timing and which store would do better for what product. I have a small store because I won't put just anything in the market and have more freestuff than mp stuff.
Another thing to consider, although it may not amount to a lot, is that once an items gets to top 30 status the percentage changes. Top selling items pay 10% less to the store where low selling items pay that extra 10%.

What the marketplace needs to do is get choosey. Deny textures that are simply flood fill that took an hour (or less) to do, require detail. Start suggesting that a simple prop, like one would find in freestuff, be either put in freestuff or included in a much larger marketplace package. Deny first time models who just followed the latest tutorial, such as a the rhino 'model a chair' tut.
Poser Pros has no problem with making suggestions to merchants about raising the potential of their products as well as taking the stand that they wont accept just anything. Nothing wrong with that.

...... Kendra