Way back in 2012, we talked about some unique pencils that write as you expect, but have a unique feature. Once these pencils are too short to write with, you can stick them in a pot of dirt, eraser end first, and they will grow plants.
That isn’t exactly cheap for pencils, but considering you can grow things out of the eraser, it may be money well spent for the novelty (and edibility) factor. The herb pack has basil, cilantro, dill, mint, parsley, sage, rosemary, and thyme. The flower pack has four each of marigold and calendula. The only catch is that these pencils have no erasers.