A lot less than you might think. Certainly a lot of work goes into pictures like Kurt Stallaert's work after the shutter button's been pressed, but almost all of what elevates them from snapshot to photograph happened on the scene. (That said, I can't see anything special in Gorbot's photos other than composition and choice of subject. Sometimes deciding when, where and why to point the camera is all the difference you need.)

Almost all fashion advertising and editorial photography uses artificial or at least auxiliary lighting, whether that comes from hot lights, flashes, or simply reflectors. Stallaert's work is a good example: each of the photographs has at least two lights on the principle subject(s) in addition to whatever is providing the overall "ambient" lighting. And that light is controlled, not just spilling everywhere — grids, snoots, barn doors, flags and gobos, the things that keep light from getting where you don't want it, are as big a part of the lighting game as the lights, reflectors, umbrellas and softboxes themselves.

Post-processing can only create a spectacular image if it was at least very good to begin with. (And remember that we were doing images that we pretty darned close to this on slide film in the old days.) Learn to see the light first when looking at work that impresses you. Try to imagine how that highlight got there and why the shadow edges look the way they do. Experiment. See how much light you need to remove to make the highlights stand out. Figure out how close you need to get the lights to have them give the effect you're seeing. When you can get ninety percent of the way there in camera, the other ten percent is easy (drudgery, but easy).