I was quoted a 2015 white, 2500, v8, hi-top, power windows, not tech pack in Portland Or for $28,000 two months ago. I ended up purchasing a used one though.
2013 2500 hi-top v8 with 40,000 on the rig. My best on the highway at 65 mph with no ac, carrying my dirt bike is 14 mpg and I really babied the throttle.
I do 5k on everything. Check out the soot in your air intake on the CLEAN side of that k&n filter. Had one on the duramax for a short time. Never again.