If I remember correctly, Canon's kit 18-55mm IS lens is very close, performance-wise, to the much-lauded 17-55mm IS zoom when zoomed out and wide open. Granted, it's a half stop slower and build quality is poorer so the theoretical mtf may not correlate with real-world performance. I also find I get a lot of chromatic aberrations around the edges, but at 18mm, this is nevertheless an excellent lens. At 55mm it's worse and obviously much slower, but not terrible. For the money and given the small size, I'm impressed.
The older 18-55mm IS is pretty decent at 18mm but soft at 55mm. And it lacks IS, which is a bummer, especially considering it's slow. I haven't had much experience with Nikon's cheapest kit lenses but I hear good things.
I think the best way to think of it is that price pays for a more esoteric need (speed, reach, zoom range, a combination of the three) than better objective performance. At least most of the time. After all, virtually anything is pretty good stopped down a bit. In addition to this, if something does just the very basics (the 35mm or 50mm f1.8 Nikon, for instance) it can perform very well for the money. The cheap kit zooms hit a nice balance between versatility and performance but don't excel at anything, so that's why there's a bias against them. They're not very exciting.
It's easier to make an exciting photo with a lens that can do tricks (ultra-fast, quick AF, ultra-wide, great bokeh, etc.) than it is to make one with a general purpose lens, but that's only because your composition and subject matter really have to stand on their own if you can't disguise them with flashy tricks. Of course, if you're an event photographer you probably need a fast zoom and if you're doing portraits you'll want something fast and long; landscapes and architecture might need a T/S lens; sports and wildlife might need a mega-zoom. So pay for the need, not for the performance (and if you're shooting billboards, performance IS the need...). I think those talented enough to let their work speak for itself will feel just as comfortable with a cheap lens as a fancy one--if the subject calls for it.