Put it another way. If at any given time you could be interested about 1 thing out of 100, if you are shown random ads, the value difference is 100x compared to if you were able to accurately identify the 1 out of 100.

So then consider that when you go to other websites, with FB code embedded within them, some of them e-commerce sites, they will be able to retarget those ads, which you already showed at least slight interest in. This is likely a huge difference.

You already showed interest in that gaming mouse, but for whatever reason you decided you would buy it later or not now, maybe forgetting all about it eventually, but then you see that ad to remind you. That's a huge difference.

Definitely yes. Non targeted ads tanks click through rates which directly reduces price per ad impression. Not surprised if this is a xx% hit.

According to some articles I found from Google, already retargeted ads (someone went to an ecommerce shop, showed interested in a product, but didn't buy it, gets shown this product on another website), already has 10x difference in CTR compared to normal display ads which I think also take into consideration your likely demographic and interests. So even larger difference between completely random ads.