Another thing everyone needs to keep in mind is that the salary cap has been flat since it's return in 2011.
It was growing by $7M per season from 2006 ($102M) to 2009 ($123M) prior to the uncapped 2010 season.
That's a $21M increase in cap space over four seasons.
The cap came back in 2011 ($120M), barely moved in 2012 ($120.6M) and increased $2.4M in 2013 ($123M).
Teams could also "borrow" up to $3M from future caps in 2011 and up to $1.5M in 2012 (the "borrowed space will be repaid from 2014-17 however a team desires).
The 2014 unadjusted cap is currently estimated at $126.3M, an increase of $3.3M, but it may end up as high as
$128M per NFP.
That's a $6.3M to $8M increase in cap space over four seasons and Dallas had to endure the Mara penalty ($10M divided over 2 yrs) the past two seasons as well.
The cap has actually gone up more than originally expected in '13 and '14, but a real increase is being anticipated in 2016.