You do realize that the value chart they use is not quite right. It appears they took one and made some adjustments to change it, but the original it was based upon had two mistakes. The two errors are in spots 19 to 21 and 33 to 34. If you look at pick 20, it costs you a middle 6th rounder to move up to 19. But, if you are at pick 21, it costs you a late 4th to move up to pick 20. Why would it cost more to move up from 21 to 20 than it does from 20 to 19. The same is true for 32-33-34. It costs twice as much to move from 34 to 33 than it does from 33 to 32.
And, just for some background, while sites may list these things as being from NFL teams, they truly are not. To my knowledge, the NFL teams that use these charts have not turned them over to anyone in the press. The information came from a news article on Jimmie Johnson. Of the 256 slots in the draft, the article touched on only 10 of the numbers associated with the draft chart. Some draftnik over at footballcorner.bizland.com (later just footballcorner.com) took those 10 numbers and built an Excel spreadsheet, plugged them in, and attempted to reverse engineer the draft chart. This was in the early 90s. When the draft site folded, he allowed access of his chart to a few other websites and it spread like wildfire. To keep from completely copying it, some made some changes on a few of the numbers, but if you see the two mistakes listed, it was based off the initial flawed chart where he made two mistakes. Here is the original .gif:
Kind of crazy how this thing has just become accepted as an NFL chart when only 10 numbers are actually off Jimmy Johnson's chart. Just thought I would throw this out.