Actually the opposite is true. A basic alarm system (installed) will usually cost around $1000.  Most systems come with an analog telephone dialer built into the unit. This will allow you to hook in a standard POTS line (hardwired phone line from the outside pole) or Comcast, and monitor with any alarm monitoring service. Such service can cost anywhere from $15 - $30 per month depending on the features offered by the alarm company. Today most companies are in the business of alarm monitoring contracts and subsidize the cost of the alarm system by requiring a multi-year alarm contract at an inflated rate. They might charge you $199.00 for the alarm system and $45.00 per month for 36 - months. So you are paying an additional $30.00 per month for your $800 savings or about $216 over the 3 year term. Not too bad if it is only 36 months (about 8%) and if you want monitoring. If you don't want monitoring you are paying $820 more over the 36 months or about 35% annual premium.

The other difficulty is that these companies usually are not alarm companies but rather marketing companies that immediately sell the contract to an ADT, Monotronic, Protection One or some other large national firm. The installation is usually pretty shoddy with poor workmanship and cheap equipment. If you have the money you are much better to use a local company and pay for the install and leave your monitoriig options open.  You can save a lot of money if you work with a company and install your own system. You jut want to make sure you use good equipment.