The math works a lot like this:
The amount required to be PAID OUT by the company is predictable: if the payout starts at age 65, the life expectancy of the person is just less than twenty years (from the actuarial tables maintained by the life insurance industry: men live to about 78, on average, and women to about 82, on average).
The question becomes "How much do we need to have, in order to make that payout, when it comes due?"
The answer is "We don't need as much, if we can hang on to the money for a long time, before we start paying it out." If the subject person is age twenty now, and we get to hang on to that money, and collect interest (compound interest, really) for the next 45 years, before we ever pay out a dime, we can do the job for a lot less money, maybe $5,000 or so. We take the $5,000, earn interest for forty years, and it has grown to about ninety thousand dollars, and then we start paying out money.
What if the subject person is age 63 right now, and we have to start paying out just two years from today? Well, then it takes a LOT more money to get the job done, doesn't it? You want us to provide an income to a 63 year old man, starting at age 65, that lasts for the rest of his life? Then bring in ninety thousand dollars, and we can do it. We're only going to get two years of interest, and then we have to start paying out, X dollars a month, for as long as he lives.
So you can see that the value of an income, a pension, is very little, if the worker is quite young, and many years from retirement, but the value of that pension is very high, if the worker is very close to retirement. Have a CPA value the particular pension in question: it's worth the money.