It's no secret that it's all pretty much the same stuff: calcium chloride and sodium carbonate (a.k.a. washing soda). Buy the CaCl in bulk and make your own washing soda from plain old baking soda.
While your at it, pick up some magnesium chloride and/or magnesium sulfate (a.k.a. Epsom salts) as well and you're well on your way.
http://www.reefkeeping.com/issues/2006-02/rhf/index.php
All you're paying for with the LFS stuff is the fancy labelling.