I posted a shot of AlanX over at Daz, rendered without any postwork. (I gave specifics of what I did, because I used the Artistic Lens thingy posted by BB here on the forums)
I know 2 people at least who went and got that character set for the texture alone, because of that render.

I rarely use the morph presets.

Also, I picked up Oman here the other day and rendered him (with my own morphs) and showed the render to my writers group.
Lets just say one of them said she wouldn't mind having triplets by this guy, no questions asked lol

A good render will sell stuff, I'm sure. If the product is solid, then there is no need for touch ups.
There is a need for a good render though. I do like products that include renders by other people with the stuff on sale.

Silke