Design roughs for a client and the value of our art...

I worked up a few roughs for a client/friend the other day and he was so funny after viewing the sketches, so pleased with them, that I had to remind him they were roughs still, and needed quite a bit of polishing. "Really?!" he asked, "Oh, ok...yeah."
Sometimes I forget that my work is valued so, even admired, when I can just whip things out! It's as I reminded my mechanic the other day to charge me what his time was worth! To him it's no big deal, easy even, but to me, he's an automobile artist! There is no way on earth that I could fix an engine! It's the same with my art I guess!
Just seems wrong somehow, to charge a fee while having a good time!