Its harder to recommend a second step pen, as it depends more on personal taste. There's two facets to what you get as you step up the price ranges - fancier nibs, and fancier bodies.
Fancier bodies is almost entirely a style thing - if you want a certain look, you can pay for it.
Nibs is a trickier thing. The "solid gold nib" thing isn't just marketing, there's actual advantages to it - mostly an opportunity to make the nib "softer" as it bends and flexes slightly as you write. This is very much a taste thing as well, but a much more difficult one to judge online! Different brands will generally have house "feels" - Lamy is a popular entry brand, and tends to make all their nibs super stiff, with almost no flex. Pilot or Sailors stlye tends to run softer.
It's also worth mentioning that Japanese brands almost all run one size "finer", so if you're looking for a nib from a European company like Lamy or Pelican that's around the size of the pilot fine, order an extra fine.
All that said, possibly my favorite nib is the pilot vanishing point, which is ~$120. I don't think there's much in the < $100 range that's significantly better than the metropolitan. I'm also a big fan of Sailor and Visconti's fancier nibs, but that's up a considerable price band.