You will see a resurgence of power leveling services, item trade services, and gold farming. Classic will have a fresh economy meaning for your average gold farmer time spent in classic is way more efficient. It will probably be worse than it was back in the day. Just look at the blizzard group finder on retail, littered with advertisements for m+ boosting websites. Disgusting. There will be so many gold farmers blizz probably won't be able to keep up. And this is what I truly fear because if the gold farmers start to win activision will step in and introduce wow token. And classic will die.
Where to get materials and reagents you may ask? Buy for cheap off farmers in bulk or track Auction House lots. Get in touch with most big sellers. Communication is important here, send a whisper or write them a letter. It would be good for both of you to establish business relationships. Constant suppliers and buyers is convenient for both parties to save the time and effort.