FOCUS: Copper TC/RCs hit decade-lows, market questions where bottom is Treatment and refining charges for copper concentrate fell again to new 10-year-lows in the week ended Friday March 12, with Fastmarketsâ copper concentrate index dropping to less than $30 per tonne/3 cents per lb for the first time. The spot market has been in a prolonged downtrend since 2014, but a recent bout of tightness has seen terms dip by 27% in the past two weeks. TC/RCs, which are discounts to exchange prices paid to smelters for processing ores into metal, are at levels last seen in 2010-11, at the tail end of a commodities supercycle, when red-hot demand for copper from China was rapidly outpacing supply.