Hello I will help you with your question,
Ford has for years built their security system around having two keys to program to the PCM. Anytime part of the security system is replaced two keys must be learned to the system or it will not allow it to be programmed to start the car.
One of the quirks of programming Fords but it is a legitimate charge as long as they provided both keys to you.
Please let me know how I can help you with this
is it fords policy to issue two keys when a person purches a used car
I doubt there is any policy when you purchase a used car, that would be decided at the time of the sale.
How much did they charge for a key?
$110 is about average for a key to be cut and programmed, I have seen $145 down to $75 so you are in the middle.
If you just purchased this vehicle from this dealer I would be speaking with the used car manager about the key situation. If this was a rental it is common for the rental company to retain the extra key when the vehicle is sold.
Please let me know what I can do to help you with this