Goaguy

I believe it is usually much higher.
That said, for flights departing Addis, the ET crew will often ensure their family members and friends are upgraded to business. This is especially true for US-bound flights but also on EU routes. So if you try and pay for a last-minute upgrade at the airport, you might end up in a fight with ET staff, as they are not happy to process it. As usual. If you want to fly C, better to book this in advance.