The in-game economy of WoW is "real" (only vendor prices are set; there's an auction house where prices are set by the players), but Blizzard has to come up with new stuff for players to burn gold with to control the predictable inflation.

To me the most blatant examples are mounts; in the last expansion they added a mount that costed 2M gold[]--when I thought it was crazy and that they couldn't possibly outmatch it, they came up with a 5M gold mount[] that was released in the next (current) expansion.

[]https://www.wowhead.com/item=137570/bloodfang-cocoon

[]https://www.wowhead.com/item=163042/reins-of-the-mighty-cara...