Interesting thoughts, thanks for sharing.
I generally think $150k is a good result from a cash cow, so I was thinking that would be a ball park figure if you viewed it that way, maybe a little less given the marginal cash cow will likely generate less. [I agree you'd start higher and work down, if someone else was initiating it.]
I've viewed trades as being worth c. 150 points in recent years, more at the start and less later, so let's say it's 180 early on.
You need to be able to make those points back over 18-23 rounds, so perhaps 8-10 per round. That would cost around $40-50k to generate, so perhaps that's another benchmark. That feels a little low, but I think it's what's the numbers suggest.
I am pretty sure I'd sell one for $75k early in the season.