No team has ever won a SB because of signing big money Free Agents, ever.There is a reason for that.
As much as everyone wants to fall in love with the big name player it is a fact of life that the NFL is a capped league, so the more you pay any one player, the worse your other 52 will be. It's an incontrovertible fact.
Secondly, adding a player that thrived in someone elses system does not guarantee they will be as good in yours. If you took a list of the 100 highest paid free agents to switch teams in the last 10 years, you would have a very hard time arguing that 20 of the 100 were better after changing teams than before.
Finally, the buying frenzy that happens when some teams start to consider these guys 'must have' despite the first 2 issues, drives their cost up, and you end up paying for what they were, when a majority of the Free Agents are at or past ther peak.
I am open to any examples of teams signing top dollar free agents that worked out that any one wants to give, but really, I see no evidence that this approach has worked since the 90s when SF and Dallas loaded up on guys chasing rings, and even then it wasn't big money guys.