How do I explain to a client that I am charging $5,000 for a project that might only take me 10 hours to complete?

[Btaliat]

This is the main reason why a freelancer needs to know how to address the clients with authority. Make sure you let them know that they are paying for your experience and expertise and not really the job you are doing or even the duration that you are using. Make sure that you are not cheap or price cheap. The experience and the expertise should pay you more than the duration and the time that you claim.