At this point I feel silly answering a question that's already been well covered by Andy and Glen, but I have already written it and so you have to read it.
You are asking a good question, one that has a lot of people trying to figure out how to handle the issues involved. First, as we all know in the old days (like two years ago) you had your day rate/hourly rate, and expenses. As part of those expenses we typically we billed film out at $35 roll (or something like that) which covered the film, processing and pickup/delivery expenses.
Now, we have digits. The (not so) conventional wisdom of clients is digits are free. Wrong. True, I don't buy digits (okay, once when you buy the card), but the film developing expense is now replaced by my time in front of a computer downloading images, doing basic processing (opening and converting raw files, adjusting levels, maybe a color or saturation tweak), and then burning the cd(s). That's my time (and skill set) which used to be regulated to a third party (the lab). How do you bill for that, it's not in your day rate or your hourly rate? You have several options, one is to have a rate per image (say $50/$100 for 100 images) or one which I've adopted for most jobs which is a flat rate per job (typically I figure in $200 which also covers basic set up and local travel). The client is still getting a deal, the final product I'm delivering is ready for use without having to get scans done.
Now, none of this involves any retouching (that's available and I bill separately), just basic batch processing and cd burning for the most part. If you expose your images properly and have sufficient experience with your camera so you have confidence in your color parameters, processing should be pretty straight forward. But it does take time, and my time and skill set are what I sell.
PS, It's funny to see how closely these expense charges match with photographers with whom I have never discussed this problem. Go figure.
Couture Model Management
900 West Avenue, Suite 423
Miami Beach, Florida 33139