The NADA and KBB don't really reflect the value of these pickups very well. As to whether or not these two examples are worth what is being asked is hard for anyone to tell without looking at them and having them checked out.
As to the LBZ, in my view they live up to the hype and the high resale value you see out of them. However I also have a 2008 Duramax with a just under 100K that has never missed a day of work either.
I don't think a 7.3 holds a candle to the LBZ except in durability, but certainly not in towing ability.
I have 75K on my 3500 and have been thinking about selling it, but I have opted to wait for the power bump in the new Duramax trucks before making the swap.