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The pin-up has been around for a very long time and it has always constituted sexy images of women not men.

Hmm. You might want to look into the history of art in other cultures before making that assumption. Many many ancient cultures (and some not so ancient) revered the male form over the female. It's only been in recent centuries that strict heterosexuality has become the norm (thanks to religious indoctrination) and pin-up art has reflected that. 

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I remember when AerySoul, AsShanim, etc came onto the Poser content scene the work they did for our Vicky figures was incredible. They got numerous requests to create the same quality fantasy work for Michael and tried it but stopped after the first attempt because it just did NOT sell. Now their content was no less than GREAT and took a lot of work and thought getting it to that point so I can imagine they would have liked getting compensated for that effort properly. When they didn't they just stopped creating content for the Mike figures. I picked up that one attempt at DAZ and it was sweet. But never saw any such work ever available again. Not worth their effort! Can't blame them.

One test case is hardly any evidence that male content doesn't sell. AerySoul does female content because that's what they enjoy doing. Maybe if they quit changing their name every 6 months then more people would be able to keep track of their work. If they enjoyed making male content then it would sell just as well, if they made what people wanted to use. Because there are at least a handful of content artists I know of personally that make their livings selling nothing but male content. I do private commissions, and have been doing them for the last 2 years. I get more commissions for M4 than any other figure, including V4. Because no one wants to make male content "cause it doesn't sell".  If male content didn't sell, then why do some items stay in the market place here for years on end? Like this character set for P6 James.

http://www.renderosity.com/mod/bcs/thomas-for-james/44082/

It's not even on clearance, and has been in the MP since 2007 or 8. If it wasn't selling it would have been gone a while ago.

Quality is what sells, not the gender.