Companion pets feed the accountwide collection systems, which flattens their price differences between realms more than any gear market.
Companion Pets (Miscellaneous)
Auction-house prices and price history for Companion Pets in MoP Classic.
114 items in Miscellaneous › Companion Pets 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.
Companion Pets listings link to price-history pages with per-realm buyout, average, and median data for Mists of Pandaria Classic.