Condition
Sealed boxes with clean corners and intact seals usually attract stronger interest than crushed, sun-faded, or heavily stickered boxes.
Completeness
For used sets, missing minifigures, rare elements, manuals, or accessories can change value quickly. Complete should mean checked, not guessed.
Demand
Some themes have deeper collector demand than others. Modular buildings, licensed themes, limited releases, and desirable display sets can remain active after retirement.
Authenticity and trust
Clear photos, accurate descriptions, and honest flaw disclosure help buyers feel confident. Vague listings can discount even desirable items.
Shipping risk
Large retired boxes are easy to damage. Local pickup, insurance, and careful packing can affect final offers and buyer interest.