For me, it's mostly a matter of the expense of ordering that many. 3 patches (two chest patches plus the shoulder patch - the usual stuff in most NGA dojos) times 100 patches makes for a total of several hundred dollars, and probably 6 years worth of patches. Thus far, all of the money I've taken in has gone into equipment. That's unlikely to change in the near future unless I add several new students, which is likewise unlikely.
If I don't find a reasonable short-run producer
Custom Patches in Houston, I'll probably skip the traditional chest patches (some symbolism within the art) and just do the shoulder patch. In a pinch, I can actually embroider the chest patches directly on the uniforms (I have a machine that can do that).