But are those increases in quality worth the relatively higher cost?
Not necessarily - it can be a bit like splitting hairs. And whereas some people will obsess about resolution, distortion, and the more measurable 'technical' characteristics, each lens model has its own character to do with how it renders - contrast, colour, bokeh, flare, ...
In other words, there's a subjective dimension.
Here's Bjørn Rørslett on the Nikkor Ai 85mm f/2 - ".. unfortunately the optical quality is nowhere in the league of its predecessor. In particular I found pictures taken with the 85/2 to be dull and life-less, and images took on a greyish cast as well. I'm aware of reports claiming this lens is an excellent perfomer and am at a loss to explain this discrepancy in opinions (I've tried several 85/2's and they all behaved in a similar manner)."
Versions of this that I've tried give the lie to those remarks, and the images from them appear to be contrasty, bright and sharp. My current one is a favourite lens on film or ff digital. So what he means by 'grey' is a complete mystery.
Explore the world of lenses, and be happy!
ps I wouldn't bother with a zoom for landscape ...