Most junk-flagged items trade near vendor price, but a handful of gray transmog pieces carry genuine collector premiums.
Junk (Miscellaneous)
Auction-house prices and price history for Junk in MoP Classic.
950 items in Miscellaneous › Junk are currently auctionable in Mists of Pandaria Classic.
Prices refresh daily from TradeSkillMaster (TSM), so day-to-day gaps in lower-volume listings are expected rather than a collection problem.
Junk listings link to price-history pages with per-realm buyout, average, and median data for Mists of Pandaria Classic.