the cost of storing an album,
the wastage if you damage an album,
the time you slot in the photos into album,
the cost of prints,
the wastage of prints,
the time you go to lab,
the transportation from home to lab, etc etc,
of course you have to make a decent profit for making the album, else you are wasting time and money doing it for free.
don't forget you are only charging couple for time on shooting a wedding, if the selling album don't cover your time and money, might as well just pass the CD to the couple ask them to print it themself.