In August 2016, when Legion was released, a WoW token was worth 35,000 gold. Prices began to rise after Blizzard announced that tokens would be redeemable for Battle.net balance, and when the new functionality was released, the price of a token surged to about 90,000 gold. In July 2018, shortly before the release of Battle for Azeroth, prices peaked above 200,000 gold per token.
Something to keep in mind as well is that this will make enchanting materials more valuable, since it is likely most players will now simply scrap their boe greens instead of getting them disenchanted. Also redundant dungeon/raid gear can be scrapped rather than traded to the (guild) enchanter in the run. Less stuff gets disenchanted, meaning there will be less ecnhanting materials, meaning their value will rise. All the more reason to DE rather than scrap as an ecnhanter.