Well I became a Weaponsmith with my Paladin a long time ago. Found it interesting, but not too usefull. To make some of the best selling weapons early on (say like Phantom Blade) you need to farm a lot or buy really expensive items. Ultimateley, you win around 5-10 gold (at least that was my case). I never got far with Weaponsmith, so I don't know the end, but for the time I had it, I didn't found it too usefull, considering how some drops were much better than what I could make.