ANot disco dust but the edible shimmer dust. How much extra should i charge? Edible diamonds?

I don't charge a penny extra to add shimmer. It is just part of what I do. Just like I don't charge to add color. I know what my costs and overhead are, and what I need to charge to make money, so I just pad that a bit, and it covers the little loose ends. Besides, a bottle or airbrush shimmer is about $4 and I can use it on about 30 cakes, so the dime doesn't hurt me at all!

If it is gold leaf, that crap is HIGH! So, I charge the cost of the leaf, but add it to my per serving price, unless it is a dab or two, on a large cake. So a small 24 serving cake, with leaf may be $4 a serving, while the same cake with shimmer may be $3.50. A large 200 serving cake with the same amount of leaf may be $3.50 a serving, while the same one with shimmer is still the same, because the $12 isn't hurting me, it is covered in my padding.

I don't charge anything to add shimmer either.

shimmer/pearl dusts = no charge.  Just part of doing business.

Edible diamonds, depends on the size.  I buy them and mark them up at least 3 times.