Cosmetic armor sells on appearance alone; transmog collectors set prices that have nothing to do with item level. Within Armor, the Cosmetic subtype gets its own tracked table here. Each row below carries its own price-history page rather than sharing a single blended entry.
Cosmetic listings clear and replenish at whatever pace the in-game market sets; some subtypes trade in volume, others sit static for stretches. The price-history chart on each row's detail page makes that pattern visible at a glance.
Use the search box on the item database home page to jump to a specific item by name, or use the breadcrumb above to step back up to the full Armor category.