First, think as to why the film photographers offered prints and didn't offer the negatives:
1) The client has no use for the negatives.
2) A good lab charged nicely to make a quality enlargement.
The drawback is that the client doesn't get ALL of their pictures. Just the ones they purchase.
So there's some film wasted, which was shot but not bought... and nobody benefits from it except the lab.
Now weddings are shot in digital.
You offer full CDs because:
1) It costs you nothing
2) The bride/groom want some picture for online galleries, emails.
3) The images have no intrinsic value to you as a photographer.
I would give away the CD.
Why? I can base my pricing structure so that my profit comes from the shooting fee. Not from the sales of the prints.
I come back from a wedding having shot 205 pictures. They only buy 5 - what do I do with the other 200? I don't need them, the clients do, but not willing to pay for it...
I'd rather charge full price up front.
