For a lot of us, the canon 5D mk iii is too expensive. If you compare features between canon $3300 paid in average for this camera is way too expensive, if you compare between canon and nikon it does make sense at all either. Honestly the real price currently for this camera should be $2500 top. Why is so high? Canon are you listening? I want this camera but I am stuck in buying the 6d!
You should buy the 6D. Its lenses where you want to invest your dollars. I bought my 5D MK III for 2750 in a Adorama deal on ebay and got enough in ebay bucks to buy a extra battery.
When you calculate the net cost of a camera, include the price of a system with similar performance and lenses. Unfortunately, many Nikon lenses cost more and are inferior, so you need to plan before you buy or suffer the consequences. Nikon does have a few very good lenses, but nothing comparible to the 24-105mmL, or the 100-400mmL, or the 400mm f/5.6L, the list of lenses that are poorer as well as more expensive is long. If you add the cost of software that is free with your canon camera as well as working better, that also levels the price.
So, decide on a system that does what you need, and then compare prices. It can go either way, depending on what you need.