Here's something I was thinking about earlier today.
Jerry Jones' ego is so out of control that he's probably costing himself billions of dollars. As you mentioned, the Cowboys are worth roughly $10 billion. Imagine if he actually turned the reins of the franchise over to competent people and let them do their jobs without his interference. The Cowboys very well may have two or three extra Super Bowls by now, which in turn would have added more value to the franchise.
I've seen this effect with other sports franchises. For instance both the Chiefs and the Golden State Warriors got a nice bump in the the value of their franchises after they rattled off multiple championships.
Imagine being so egotistical that you'd rather chase credit for a ring rather than have an extra $2 - $4 billion in your bank account.