Ha ha - great question! These days I would say the most expensive one is the one you don't get. Burglaries are up, bad guys are stealing more stuff, and alarm systems do a lot more than they used to. Plus, the rebate you get on your homeowner insurance should offset a chunk of the monthly fee, especially if you add fire monitoring(should not cost extra). Throw in getting rid of your phone line (good alarm systems are cellular), and you are there. As for fire, my wife is more worried about our two dogs than someone stealing anything, so we have smokes on all 3 floors. Our dogs do not dial 911 that well... Here is an example of what some good systems offer: 1) 100% cellular monitoring - no phone line required, and none to cut! 2) Remote arm/disarm capability 3) Special apps for iPhone, Blackberry, Android 4) Email & test notifications on anything happening at home: doors opening, etc. 5) Video services - live viewing from any web connection (including phone) and motion-activated clips 6) Smart home - remote light and thermostat control The world of alarms has changed, as you can see - and all this does not have to cost a lot. Shop hard, check the reputation of any company you consider, and take your time. Good luck!