Yeah, this post is bizarre. Between "I bought an expensive $40 security system" and "it needed the internet, so I got rid of it and built my own, which also required the internet", I don't know what to think.
The post said that the commercial security system required "broadband Internet", which had a much higher monthly cost than the existing lower-speed Internet connection.
According to the post, the commercial system demanded a $100 monthly cost for the security services and broadband Internet, vs. $5 monthly cost for a lower-speed Internet access that was enough for the custom solution.
Therefore the reduction in the monthly expenses was worthwhile.