Simply providing a client with what they want is good, but not the best business practice. If you can expand what they want with what they could have, then you're leaving the door open for more work in the future. The truth is, most of the time the client doesn't know what they want because they barely know what is possible. It is you're job to inform them of the scope of possibilities.
I recently had meeting with a client which initially only wanted a short 3 minute promo video. By the end of the meeting they were convinced to start with a 2 minute promo, fallowed by an additional 10 minute in depth descriptive video to be produced later on. By using the strategy just mentioned I effectively increased their initial budget and potentially doubled the amount I could earn from the client.