The pricing factors collectors check first
Fountain pen pricing is rarely a single brand lookup. The same maker can sell across a wide range when the model, nib, filling system, and repair risk point in different directions.
Nib material and feel
Gold, flexible, broad, stub, and music nibs often carry premiums when the nib is usable and not sprung.
Filling system risk
Vacumatic, piston, snorkel, and lever systems need service assumptions when the sac, seal, or diaphragm is unknown.
Model demand
Parker 51, Montblanc 149, Sheaffer Balance, Pelikan piston fillers, and overlay Watermans price differently from generic pens.
Condition proof
Cracks, cap lip damage, personalization, plating loss, and missing boxes can move a pen from collector range to quick-sale range.