I just harvested my tree saplings today following this guide perfectly. Here's what I spent doing this:
1 stack of tree saplings: -120,000 Gil
10 Porcelain Flowerpots: 10 X 6000 = -60,000 Gil
4 Tables: -2,000 Gil
Total Spent Trying to Grow Fire Ores: 182,000 Gil
What I got:
many many stacks of cinnamon, all of which I will NPC (not sure how many stacks exactly since I was kicked off shortly after harvesting due to scheduled maintenance)
6 ice clusters = crap
1 fire ore = 200,000 Gil
Net cash inflow: 18,000 Gil or so
Time Spent trying this: 1 month of checking plants twice a day (once in morning, once at night)
To me, this isn't really worth it, but I'm thinking maybe I just got the shaft on one single ore from harvesting...but I'll leave my results with you to decide if it's worth it or not...personally I'd rather go back and hunt the Valkurm Emperor