They left something out in the OP article.
They saved money on the cap trading Jones.
From
MMQB.
So the full value of the trade is Thuney, Mitchell, Cooper and $5.41M in cap space.
The MMQB article cites Long and an additional $1.7M in cap space as being what that $5.41M represents.
However, there's another person to consider.
Bennett's cap hit this year is $5.185M, so you could remove Long and put Bennett at $0 on the cap as we got for trading Jones.
So even if you go with the MMQB list, I think Thuney, Mitchell, and Long for Jones is a pretty good deal.
If instead you say it allowed us to afford Bennett, it's even a better deal.