"It depends on the size of the wish. They come in eight known kinds, the objects different shapes with different numbers of points from three to ten. The smallest two sorts are easy to make. I produce them every day as a matter of course. I would not care to try to make anything larger except in direst emergency; I have a supply, from my friends, but they cannot reach me with more right now and I do not know how long it will be before I can see them again. An ordinary human - or elf - cannot make the kinds with eight, nine, or ten points; the requirements are beyond the limit of what you can feel without some sort of change to how you work. And maintaining the concentration to make a six-pointed coin, let alone a seven-pointed coin, while suffering the requisite discomfort, would take considerable effort for most people."