Blacksmith is very expensive as you constantly use iron up to rank 41. Iron nuggets on cornelia sell for 1.2K-2K each. Then on top of that the shards/crystals. Silver nuggets are selling for 5K each and a 3 per synth it is very expensive. This is why i have started mining my own mats. I would suggets to anyone wanting to seriously take up blacksmith to do mining aswell unless you have millions of gil to waste on mats.