cash costs and margins

Hi BSE followers,

Just a couple of questions for those who follow BSE in depth. I was reading their presentation and there was a page which states their cash cost to be ~$4per/tonne with a margin of ~$10per/tonne. My question is I thought their sands products has a market sell value in the thousands of dollars per tonne, so what is meant by the fact that they make a margin of ~$10 per tonner.

I am a newbie to sand minerals type company.

cheers