Crawford signed a new deal in the Spring of 2015 that called for him to be paid $45,675,000 over the next 6 season, from 2015 thru 2020. That deal averages $7,612,500 per season, not $10M per year. The deal was based on him playing the 3-tech DT position. Because of injuries, and suspensions, Crawford was pressed into duty at DE, where he grades out as an above average Dline player, but certainly NOT high quality or Elite. Elite DE's get paid $17M per season, not $7.6M per season. Until some younger player displaces him as a starter, he may be slightly overpaid. But when you consider how he doesn't get hurt, and how much the NFL is paying for players like Hitchens, his salary is not as far out of line as you might think.
Now, do the Cowboys need an upgrade? ABSOLUTELY!! That's why they spent a 2nd round pick on Randy Gregory and a 1st round pick on Taco Charlton, and a very high 4th round pick on Charles Tapper. But to date, not one of them has been able to play as consistently good as Crawford. It's one thing to complain about Crawford. It's another to realize the Cowboys have spent 3 premium draft picks trying to upgrade him, and none of those picks has panned out...yet.