Probably should change the title to "Complimentary upgrade value for DL Diamond nears zero"
The CB's alone for me (estimate $300 per RUC's, and $1,500 per GUC's) are $7,200 based on my perception of value, not the price difference to an overpriced last minute F or J fare.
I always value complimentary upgrades at zero. They are lottery tickets.
DL gives extra CB's at $50k and higher of spend, but wasn't worth it to me when I keep status in 2 programs.