Remember that most taxi drivers who operate on the street, not from the tourist hotels, don't own their cars. They might make 120 Egyptian pounds a day and give half to the car owner. A kind tourist who pays 50 Egyptian pounds instead of 20 for the trip might mean the driver can buy a kilo of meat for the family at home.
Cairo is hard for middle-aged fathers who have to work all hours to pay for tuition for their kids. Remember that the next time you think you are being fleeced and pay extra to the decent ones. They deserve it.