Well, Anaconda, since the idea is that I'll be forging items that you probably can't get on your own without a great deal of investment anyway, I think it's fair to ask a pretty hefty sum of gold in return for my services, say a baseline of 50 gold per magic level required for the crafting? And say, double that amount for boosters, since they're so much more valuable. So a Weightless Scalemail or Chainmail of Displacement would cost 100 gold, and a Winged Helm would run you 400. I think that's pretty reasonable.
Of course, I'd have to charge more for Water and Nature items, since I have less mages with those paths. Maybe an extra 25 gold per level for those items. So... 225 for a Wave Breaker, for example.
Of course, this is open to haggling and you may want to bribe me with gems, instead.