Well the average income is not that high, but the 'middle-class' are very wealthy, and make up a significant part of the population. I know there were charters between Cairo and Malaga, but wasn't too sure about flights to Palma.
I also think that Spanish tourists use this service during the winter, during Egypt's peak holiday season. They probably stay a few days in Cairo then connect with flights to Luxor, Sharm El Sheikh , Hurghada, etc.
I guess the charters are for Egyptians in the summer, and Spaniards in the winter. Do Spanish airlines also operate on the route, or do Egyptian carriers have a monopoly on the route?
EGYPT: A 7,000 Year Old Civilisation