Santoro - YOU are the one taking the risk on this, so I say go with your gut feeling. Also, discuss with others (such as Peale with his black start buttons) the risks associated with a custom run. If you do a run of Brass AND a run of Nickel, would the per unit cost would drop since the die costs are spread over more tokens? However, yes, you are assuming a higher upfront cost and you should be compensated for that risk. If you just stick with the small brass run, you only have to sell 25 lots of 200 (if my math is right) and if half of the people participating in this order, you should be well on your way to having them all sold. Question then comes up if you do a second run, do those people get a price break since the dies are already paid for?
Kudos for doing this and I'm glad I'm not the one ultimately burdened by these decisions.
Oh, I voted for brass because I think they'd look nicer polished and put in a nice display frame.