My brother built a wedding photography business in ~2008. He filled out the entire first summer of bookings with $50 of highly targeted facebook ads (female, engaged, 200mi radius).

The same ads today would be much more competitive, but there's a huge amount of leverage here.

Facebook ads were so underpriced for a while, you could get 10x ROI. Nowadays you get what you pay for.

One way is through re-targetting. You visit an e-commerce site looking for a pair of shoes. You browse for a while but nothing seems interesting so you leave. The site then targets you through Facebook with tailor made ads and probably limited time discounts. They can track you through Facebook pixel. It works like a charm because the need to buy the product never went away.

A large portion of users do indeed block ads, but most don't. The higher blocking percentage I've seen is in the region of 30%-35% (it's in Greece I think).

What portion of targeted Facebook ads are blocked?

What portion of facebook apps are scrolled past by people who instinctively ignore "suggested posts" or are otherwise scrolling to find a post that was just there a minute ago?

Once I was looking for an event post to check what time it was at, and ended up scrolling for a while trying to find it, meanwhile thinking about how facebook is getting paid for every ad impression I'm zooming past...