Shouldn't we add the lens cost?
agreed, I have the 17-40mm and 100mm F/2.0 with a few other lens. Nikon enthusiast lens are typically more expensive across the board. But that's not even the whole problem, the other side of it is that Canon has made many more lens total so the used market is much more competitive Canon wise than Nikon wise.
Nikon has nothing affordable for Ultra wide and all the ultra wides besides the 14-24mm are not very good.
I suppose if you looking at the highest tier lens the gap is a little less pronounced but for mid grade enthusiast/pro lens Canon simply has a far better selection.
I mean it was only till recently that Nikon even had ANY competitor to the 100mm F/2.0, their 85mm F/1.8 with a ultra sonic motor didn't come out until last year, so if you want that lens you are forced into buying a new one since there would be so few in the wild.