Patch 7.3 adds new crafting materials for every professions, and if I remember correctly, this is the first time new base materials were added to the game this late and not just at the start of the expansion. You should expect that these will be really expensive at first.
These materials are:
I made farming guides for all of these new materials so check them out if you want to farm them. But keep in mind that most of these farming places will probably be pretty crowded, since everyone want these new materials