It makes more sense to sign contributors at a value price.
The Cowboys greatest flaw in the past when it comes to free agency is the mentality that signing a certain players to a large contract has effectively filled that position.
The issue is twofold:
1. The team is one play away from going right back to where they were before except now they can't afford ti pay another effective player due to the cap hit at that position. They must now rely on that player's minimum wage backup.
2. Now that the player is signed, he is now the designated starter due to the money and the lack of serious competition from the minimum wage backup. There is nobody to push him and make him more competitive. Even the most competitive player must feel pushed by another who wants his job.
Conversely, the backup feels there is no upward mobility, he has no chance of replacing a guy that his team has placed a financial commitment with. His competitive edge is also compromised.
The bottom line is that when you need to "fill a hole" at a specific position then you don't require one player, you require at least two capable of playing at a high level. Large free agent contracts produce an uneven distribution of cap space that makes this highly unlikely.