Someone on Reddit shared how he built a system that auto-generates reaction-style marketing videos using AI.
It scrapes viral TikToks, figures out why they blew up, generates AI reaction clips with text overlays and product b-roll, then auto-posts across 12 TikTok and Instagram accounts.
Results after one month? 8.7 million views. One video alone hit 5.3M 
Cost per video? About $1.
His approach 
When a format works, milk it with lots of variations and copy it across all accounts.
The trick is narrowing the automation to a very specific type of content. You can clone the automation for different content, but each have their own skill file.
Doing this manually would cost a lot more…
Hiring someone instead of automating it would add (at least) $500 per person per month. Might need 2 people to manage those accounts.
That’s $1,000+/month – replaced by ~$1 per video 
Could be a neat agency play: set up AI video pipelines for brands, charge $1,000-2,000/month, and your actual costs are a few hundred bucks 