Nice responses. Taking a quick work break to check in and offer a few more thoughts.
In addition to the other reasons for trading down more often than not(maximizing opportunity value of the selection)......
There's a few other reasons I favor the strategy.......
In this era of FA, I believe your better off having two teirs of players:
Tier A are established star types earning about 8 mil on average on their 2nd NFL contract. These obviously can be your own previous selections you've resigned and other teams players who hit the market.
10 of these players would take up 80 mil in cap space. That only leaves you 45 mil to pay the other 43 players that would fall into Tier B. Almost all those players need to be 1st contract players, age 26 or younger.
If you're consistently trading down year after year, you're consistently adding 2-4 extra selections, therefor increasing the number of good young prospects you bring in each season.
IF you do this well, you seldom if ever should get caught in the spot we are now in with Spencer. Making him a true Tier A highly compensated vet when he isn't really special.
You almost always have a younger option or two you can trust and let that slightly above average player get over paid by someone else.