My understanding is that around 50% of the contained HREO value...

My understanding is that around 50% of the contained HREO value would report to the miner and 50% would report to the processor. Transport costs would be minimal.

Thus if you had a basket price of $4000 per 1% HREO around $2000 of this would go the miner and subtract mining + concentrator costs + overheads to create the profit.

The 0.2% cutoff represents $400/t [using published HREO prices at that time] to the miner and for remote open cut with a simple flowsheet this should work as the average grade will be above this figure.