There is a big difference in the trades that the draft compensation & salary cap considerations don't take into consideration.
Context: Rams traded mid season for a critical piece that was needed to get to the Super Bowl. You might spend a little more when you are so close and think that a trade is all you need. You also pay extra when you don't have to take the cap hit for the players salary.
Mack trade is made off season and is part of many variables in play as the Chargers build their roster. Mack was and still may be a great player but Chicago is basically saying he isn't worth the much money against the cap. Now the trade may work out well for SD but Chicago must know something as he is the highest paid player on defense, at least until AD redoes his contract.
Did the Rams over pay? Heck no the plan worked and we won the Super Bowl. Time will tell how the Mack trade works out.
