Most alarm companies offer a "package deal",,,IOW, "we will arm two doors and three windows, one key pad, one alarm box, etc. for $99.95 and then you pay the monthly service fee. If you want to add other doors, they are about $150 per door and something else like $100 per additional window. So, a large home with lots of doors and dozens of windows would cost a fortune. Also, newer homes that are already pre-wired cost much less to arm than an older home where the installation process has to start from scratch. The Ramseys obviously could have afforded it no matter what the cost, but probably only chose to arm conspicuous access points since they felt Boulder was reasonably safe.