Coal prices on the open market have nothing to do with their financial problems. Eskom doesn't buy coal on the market, it buys coal from mines that are 'tied' to it. These are generally mines right next to the power plant and have long term contracts at about one third the price of the market.
Diesel fuel costs about R3.00/kWh so whenever a coal plant goes down, the cost of Electricity for Eskom goes from R0.20 to R3.00 -- they go from making money when they sell electricity to losing lots of money for every single unit that gets used. They would probably like to do more load shedding, but the government (especially the War Room) has told them not to. It promised then R20bn 6 months ago, but is not coming up with the goods, and so it has now told them to ask NERSA for a quicker, bigger price rise.
(FYI - it easy to see something fishy in the 'diesel deals with dentists' etc, but still you're arguing about them paying R10.00 or R10.20 per litre of diesel, which is pennies on the pound compared with the route of the problem == having to use diesel in volume at all!)
You can deny that Eskom is running out of money, but that won't make it so!