If you start when you're 20 (so 40 years of compounding time for a retirement age of 60), a $500 monthly savings contribution, on a 5% growth of stock investment (which, tbh, is low for such a long period), should net you some $745k (with $240k contributed, $500k interest earnings).
Is $500 a month of contributions a lot? I dont know - it depends on your income. But i think for a large portion of the working population, this is doable. It does mean sacrifice if your income is on the low end - you don't ever go on a holiday, you don't drive a new car (but instead, buy an old one so you don't have debt to service). You probably won't own property, and will continue to rent (and i'd include rent costs in the $25k in retirement cost per anum). It's not a fancy lifestyle - but it does mean you don't rely on a gov't social security, you don't rely on a pension fund that could go away.
And the end result is you will have some money left over when you die to contribute to either your children if you got any, or choose to donate/contribute to a cause you find worthy.
Under a pension plan, the person who dies early then leaves their children behind with nothing (or lost the contributions they would've deserved had they remained alive - albeit subsidizing somebody else's longer life). I don't find that fair, since a pension is part of your employment compensation, and yet you don't extract it all if you died, and thus you actually lose out.