As with most, it's a matter of degree. Taking your example, next year Starks is a $3.75 mil cap hit with a $.75 mil dead cap liability. Do you think maybe they could cut him and replace his production with someone else for $3 mil? I do.
Well, if you wanted a back in the draft who can run, catch and block in week 1 who could replace Starks' 1,000 yds. from scrimmage last season, you'd need to make a day 1 or day 2 pick, if you could find that guy at all. Who would you have not drafted instead? Even then, these college backs you might count on as a runner usually take a year or two to get up to snuff in catching or blocking. Then there's the question of whether that guy would immediately take to the blocking scheme.
Looking at FAs, who would you prefer at a lower price who can run, catch and block, can be relied upon to be productive in this system given the need for Lacy insurance, is coming off an injury-free 1,000 yards-from-scrimmage season, and could be limited to a 2 year contract? Good luck.
There may be a slight premium in this contract given the Lacy insurance factor in 3 dimensions: conditioning, performance and free agency.
Of course, it is axiomatic in the league that backs are done by age 30. This arises from the fact that early-career-high- mileage bell cows typically go into decline in their second contract if not before. Starks is a low mileage guy where the touches have been spread out. He looked just as strong, quick and fast last season as he did in 2010.
Speaking of 2010, there's something else about Starks to consider that you won't get with most FA backs...he proved himself to be a money player in the Super Bowl run.
It's no coincidence that Starks' deal overlaps exactly Lacy's FA season, which will likely be a big issue regardless of what Lacy does in 2016. If his conditioning relapses, you won't want to bring him back. If he returns to form how much can he be trusted with a substantial second contract? It's the rule rather the exception that guys who struggle with conditioning early in their careers, getting by on "genetics" as his trainer put it, struggle with it throughout their careers.
So think about this:
If Lacy is not resigned, the Packers will go day 2 in the 2017 draft for a running back. That guy will likely need work in getting up to snuff with his catching and blocking. Maybe he even struggles adapting to the blocking scheme, with the Packers left without the 2-down back they thought they drafted. Maybe he's even an outright bust like Alex Green (3rd. round) or a semi-bust like Brandon Jackson (2nd. round) who was never more than a 3rd. down back.
Starks has demonstrated he can be productive as a #1, even if it hasn't been for a full season. Then again, this fact is the reason he has low mileage, which makes him a "younger" player than his birth date indicates.
So, Starks isn't being paid a 1 year insurance premium, it's for 2 years. The price goes up. I find it a price worth paying when weighing all the considerations.