Just as example:
At release rares were probably the most profitable thing in the game. Then they nerfed it and buffed trading and combat. They also added biowaste hauling which was the new most profitable thing. 6 different unbalanced additions later void opals make everyone a millionaire and most people only know rares from unlocking Engineers...
Just to clarify, rares was not the most profitable thing, was around 14-24k profit per tonne, however, you had to factor the 150+ LY trip, and spawn times. The issue was the early bugs in a few of the stations, spawning massive amounts or rare goods. Devs quickly sorted it out after a few days. I made around 40 million from that, a massive profit in those days.
Biowaste was only profitable from a handful of ports, all of those required long haul travel back to the bubble, and high rep, also Elite rank trade status for the high paying runs. Still, a good way to make credits, 120-200 million credits per round trip. Normally about an hour or so to complete the run to agricultural ports in the bubble.
Most of the others, blatent cheating by Cmdrs, devs let it ride for a while. The long haul pax runs & Seeking goods is the only other high profits I can think of that didn't involve some sort of cheating.