Nails were chosen for few reasons:
1: Light in weight and useed in many things.
In real life you can't carry 10,000 nails on your back, first weight and then size.
This is the real problem not using dollars as currency in Xsyon.
Change nails to have more weight, then see if that is going to make nails as currency.
Nails should be = to iron weight.
For example:
One kilo of iron to make 50 nails.
50 nails = 800 milligrams when crafted.