I sell SEBA for 285c (hand trade), refined rock for 3c (shop stand) and refined gleam for 5c (shop stand).
Math says that’s 55.8c per unit. Spark is negligible. Also I have a soft spot for morgan the dude hooked me up 
If anyone is working on this order say something as I plan to fill it (slightly) below asking price. I have to craft the marble though. It will be ready in <2 hours.