While the message to save is a good one, and compounding and market growth can of course make a substantial difference, it's possible that Fidelity is being a trifle optimistic in its projections.

It's assuming that the individual or household "increases deferral rate by 1 percent at age 35, continues saving until retirement age 67, lives through age 93, and receives a 1.5 percent real (inflation-adjusted) increase in wages per year. Rate of return is 7 percent and consists of 4.5 percent real return and 2.5 percent inflation." 

It also assumes no loans or hardship withdrawals and a constant rate of saving throughout the worker's career, while not counting taxes or account fees or expenses. 

Still, pushing people to save more — even with overly cheery projections — appears to have the desired effect. 

Fidelity asked in its "America Saves" poll how much people thought that $50 per month would add up to if it were saved and invested over a 25-year period. The median response was $17,000, while Fidelity's estimate was $40,000 (again, based on a 7 percent annual rate of return, no loans or withdrawals and constant rate of saving). 

When people heard the higher estimate, it impressed them; 74 percent of those who were still working said that being aware of the higher figure made them more likely to save more. And in hindsight, 82 percent of retirees said they would have saved that much if they had known how much it could add up to.

When trying to convince people to save more, the good news is that 1 percent doesn't seem intimidating. And the promise of more money in retirement is a draw, too; the poll found that 81 percent of respondents said they'd brownbag it at work once a week if it meant they could have dinner out at a restaurant once a week after they've retired.