Don't forget also that it depends if it is a matte, metal or non-matte pigment.
There is a lot less in a pigment jar of a matte or metal pigment, so the quantity is worth more.
So, limited and rare + texture of the pigment will make the value of 1/2 tsp vary and go up.
Minmium: $4 to a lot more for All-girl for example.
Hope this helps!