What may help you is having a before and after album. Produce say, a half-dozen images and edit them to the highest standard you can. Place them in an album with the edited version opposite the original and separated by a blank page (so that when they look at the original image, the edited version is not visible). Now, start your pitch: "Here's an image from a session with Susy; as you can see, there are some issues with her skin/hair/eyes/etc. (Point out all of the issues) Of course she's a pretty girl, but no one ever looks as good as they can right out of the camera. Because I want my clients to leave here with images that are as beautiful as they are, I ONLY provide you with the absolute most finely enhanced (Never use words like 'edit', 'touched-up' etc) images I can. Now of course, this level of craftsmanship does cost a little more, but all quality products do."
I still feel (and I don't mean this to sound rude) that with a little more work and practice on the front-end, you could really reduce your editing time.