Of course it is. But many employers will want that asset cheaper than in a younger package, and some other employers will pass at any price. And that's fair, because the older developer has fewer potential years to give to the company.
"The older developer has fewer potential years to give to the company."
That 58 year old developer probably won't reach retirement age for many years. Even if they retire promptly at 65 (which fewer people are doing these days), that would potentially be seven years of employment with the company that hired them. How many young developers expect to stay at the same company for seven years? (Talking about employees here; obviously if you're a founder, it's different.)
