Why are Nikon lenses so cheap? Compared to say Canon?

I'm learning of the Nikon lenses and while their zooms are expensive their primes are so cnfusing. Why is there a 50mm 1.2 for 600 or even 400$ on eBay! And 50mm 1.4 for 200$ on eBay.these are interestin pg because they look like the old school lenses you saw in the 50s so I'm terribly confused. They look kind of like Zeiss or Leicas but I don't know how to buy a lens ror my Dx because I'm so confused. My D7000 has a build in autofocusing motor so does that mean it could autofocus if the lens can't which I assume some of these can't. Why is it so confusing? They look cool but it seems like they were meant for the DSLR.

Added (1). Werent meant.

Here are two links to both Nikon and Canon websites.

As you will see, your assumptions may be off.

http://www.nikonusa.com/...index.page

http://www.usa.canon.com/...ens_lineup

Without links to the lenses in question that will be hard to tell.

Very likely these are very old lenses though, that won't autofocus at all, not even on cameras with an autofocus motor, as they don't have an internal mechanism for autofocus (Ai lenses).
Some of these might even be non-Ai lenses, which means that the light meter of the camera won't work; and with Ai lenses the light meter of only the higher end models still works (your D7000 is one of them)

Here is a list of what lens types is compatible with which Nikon camera:
http://www.kenrockwell.com/...y-lens.htm
Note that while Ai lenses are listed as "OK" for your D7000 there, don't interprete that to mean that they would autofocus as "no AF" is explicitly listed elsewhere. The OK means that they work as designed on your D7000, and that design doesn't happen to include autofocus. "no AF" is only listed for lenses which by design could autofocus if they are used on the correct camera.

What you need are Nikon AF or AF-S lenses. These all will work perfectly on your camera, including autofocus. Any Nikon brand lenses that don't say AF or AF-S in their name won't autofocus on your camera. Basically AF means that the lens has a mechanism that the autofocus motor of the camera can use to autofocus it, and AF-S means that the lens has its own autofocus motor that is electronically controlled from the camera (as opposed to the mechanical connection of the AF ones)

Those lenses that you saw are cheap because of these serious drawbacks. The up to date ones aren't any cheaper than those made by Canon.

I'd be very wary about buying lenses on ebay. You don't know how they have been treated in the past, if there are scratches or the coating damaged, if they have been dropped and so on.

Your problem is you are looking at ebay… Compare them at the store instead.