Let's say an average of 30 hours of consumption per week per person. [1] In a household of 4 people, that's 120 hours per week.
"[Nielsen says the average commercial minutes per hour] was 16 minutes/8 seconds for cable network programming." [2]
Assuming 30 second commercials, that's 32 commercials per hour, or 3,840 impressions per week. Across 30 days, that comes out to be 16,457 impressions.
"$24.76 - The average cost of a thousand impressions for a 30-second commercial in broadcast prime time in 2014, down from $25.06 in 2013." [3]
$24.76 per mille * 16.457 mille views/month/household = $407. That feels unreasonably high. If the CPM were $2, it would still translate to $40/month.
[1] https://www.marketingcharts.com/featured-24817
[2] https://www.mediapost.com/publications/article/308248/shorte...
[3] http://adage.com/article/news/costs-ad-prices-tv-mobile-bill...