Locksmiths (the ones I know) make a little retail markup on selling locks. If you go to the Big Box store and buy your own deadbolt, they won't be as happy about installing it.
I've got some Cetron video tapes that I got a couple years ago, and recorded over many times. How about I bring them in to you and you can record some of your studio masters onto them for me? I can save a couple bucks on blank tapes, and then complain when the quality comes out crappy. (That's the kind of feeling locksmiths get when you ask them to install this lock you bought.)