Those comparisons are hardly like-with-like.   With Poser Pro, the gamma option is one of a number of options to be applied at the point of creation of the basic image.   In Photoshop, the tools are for the manipulation of that basic image, i.e. after its creation.   They aren't doing the same thing and to expect any level of Poser to duplicate Photoshop's features is ridiculous.   I have a pretty long-in-the-tooth version of PS which was far from cheap - I don't think it has got any less dear in the meantime.

Who ever said Poser Pro was a replacement for Photoshop???