OK - decided to put my money where my mouth is and see if my concept might be workable.
Here's what I propose (too lazy to work it into a grid though)
The high salary of the very top pick is what lowers the value of that top pick - yet the top pick no doubt retains value as, by definition, the top pick.
So I've worked a "discount factor" into the draft trade chart.
The discount factor is a multiplyer, subtracted from the current trade chart value.
The top pick is reduced by 10% (i.e. multiply by .10, and subtract that from the 3000 - giving you a value of 2700)
After the top pick the multipliers begin to go down, eventually weaning out by pick 13, when the salaries somewhat normalize.
Picks #2-4 are discounted by 8%
Picks 5-6 by 6%
Picks 7-8 by 5%
Pick 9 by 4%
Pick 10 by 3%
Pick 11 by 2%
Pick 12 by 1%
Pick 13 reverts to the existing trade chart as salaries don't appear to be so outrageously inflated there and further back in the draft.
So in terms of actual trade value - here's what I get for the top 13 picks (assuming my math is right:
13. 1150 (which is the existing trade value chart)
The high salary discount factors can be played around with a bit, but you get the concept. This retains the value for the higher picks, discounts heavier the higher in the draft, and eventually weans out at 13.
Looking at the Dallas picks for example, where they currently don't quite make it to being equal to #7 (1440 total - to #15's 1500 points) under the "High Salary Discount Trade Chart" they have just OVER what it would take to get to #7 and begin to appropach #6.
Tweak this how you like - I think a lot depends on how over-inflated you deem rookie salaries to be. Personally I think its mainly the top 4 picks that are most onerous - after that, value comes back into play and the salaries are high, but not outrageous (top picks have ALWAYS been relatively expensive anyways).