Travel agent is quoting a ludicrous amount for the upgrade. Something along the lines of R62,000 out of his pocket, making the total ticket price R74,000 (the normal J Flex ticket DUR-CDG is about R40,000).

I told him not not to pay this and said that I would work something out and get back to him.

I would upgrade with miles but there is only availability on the DXB-DUR leg for ~46,000 miles, which also seems excessive, though the ticket is Y flex.