The cost of residental alarm systems can vary a lot depending on the brand, features, size of the system, etc. Basic alarm systems can start at around tens of dollars, while more advanced systems with additional components and features can range from $100 to $1000 or more. Additionally, there may be additional costs for professional installation, monthly monitoring fees, and optional add-ons. If you're looking for an affordable but quality alarm security system for homes, explore eufy alarms which cost only over 100 dollars to provide comprehensive security protection.