They are photographs. Most are not edited at all. I call them textures because that's what 3D artists would refer to them as. You don't need seamless textures or even brightness corrected images when working in a 3D package.
Also, most artists would rather work from the original data as this gives you the best quality in the final image. If I color corrected the images, or made them seamless, that might compromise the final art if the artist needs the image to be different.
If this was a CD that had 1500 GAME textures on it, it'd be a hell of a lot more than $100. :-) Do you know how long it would take me to produce that many? Jeez... Unreal itself probably only has 500 textures in it. :-)
Also, most artists would rather work from the original data as this gives you the best quality in the final image. If I color corrected the images, or made them seamless, that might compromise the final art if the artist needs the image to be different.
If this was a CD that had 1500 GAME textures on it, it'd be a hell of a lot more than $100. :-) Do you know how long it would take me to produce that many? Jeez... Unreal itself probably only has 500 textures in it. :-)