They (Bingley sisters) were rather handsome, had been educated in one of the first private seminaries in town, had a fortune of twenty thousand pounds...

I have always assumed they had 20,000 each (as I see a big difference between Miss King and her 10,000 pounds in terms of social cachet, etc.) but I supposed it could be read they had a total of 20,000 for 10,000 each.