The Boston Herald, citing friends of the player, reported that Mankins, who has skipped all of the Patriots' offseason workouts, has saved most of the $7 million he has earned in his five years in the NFL and thus would not feel the financial pressure to end his holdout.
The newspaper reported that Mankins' ranch is paid for and has few operating costs.
Mankins hasn't heard from the Patriots since May, agent Frank Bauer has told reporters.
Mankins, a two-time Pro Bowler, would have been an unrestricted free agent under the rules of the last collective bargaining agreement. However, when the owners opted out of the deal, triggering 2010's uncapped year, only players with six years in the NFL gained unrestricted status.
Mankins has refused to sign his $3.26 million tender offer from the Patriots.
If he does not report to the team before Week 10, Mankins will not get credit for having played this season, which means he could be in the same situation next season. However, if a new CBA is approved that reverts free-agency rules to players needing four years of experience instead of six, Mankins would become an unrestricted free agent.
While few would argue that the Patriots aren't hurt by the absence of Mankins -- one of the toughest, most durable players on the team -- the club hasn't missed a beat through two preseason games.
With Mankins yet to report and offensive lineman Nick Kaczur, his potential replacement, reportedly sidelined by back surgery, the Patriots have turned to five-year veteran Dan Connolly at left guard.
Bauer told The Boston Globe earlier this month that the dispute has done damage.
"They have totally lost this player mentally," Bauer told the newspaper. "For this young man to work like he has and play for the club for five years, and be promised he'd be taken care of, and to throw the offer they did across the table? It was never, ever a five-year deal. They wanted six years, they wanted seven. They have to do what they have to do, and we'll do what we have to do."
In an interview with ESPNBoston.com's Mike Reiss in June, Mankins said "I want to be traded. I don't need to be here anymore."
According to reports, Mankins is seeking a deal similar to the Saints' Jahri Evans, who received a seven-year, $56.7 million contract this offseason.
Information from ESPNBoston.com's Mike Reiss and ESPN.com's Tim Graham was used in this report.