"Although now with the new ripoff fee structure I do not believe it ever makes sense to add pages anymore. You might as well renew even if you passport is valid for another 8 years because adding pages at $82 for 24 pages costs you $3.41 per page whereas renewing your passport and requesting a 48 page passport yields 48 pages for $110 which is only $2.29 per page. "

The math is right, but only if there are no visas inside to worry about replacing!

The visas from many countries last only as long as the current passport is valid (or less), so getting a new passport can be extremely expensive and inconvenient if one has already gone through the bureaucratic process of getting a visa from, say, Saudi Arabia or India or Brazil. Even a simple one like Chile's, while not requiring any annoying mail-in shenanigans in advance (it's done right at the airport upon arrival), is only good for one passport (and it's over a hundred bucks!).

So it's good to know that provided the original passport is in decent shape one can get multiple additions of visa pages.

Thanks to all you participated in this thread. It answered my question perfectly.