Well, I finally discovered why I am able to get views that cost almost nothing.
Turns out that the lowest bid you can place for a discovery ad click is one cent. However, this seems to be the same for any currency.
I have a google ads account based in USD that I have never used. Today I created a discovery ad and it wouldn't let me go less than one cent on my bid.
I also have other accounts based in Mexican pesos. I can also make a minimum bid there of one cent. but I have been getting an average cost per click of 3 to 4 cents. Anything less than that and I get no impressions.
The vital point here is that Mexican pesos are crap when compared to the USD, since it is almost 20 to 1. That means that mi cost of 3 Mexican cents is equal to... 0.0015 USD!
To sum it up, if you want cheap clicks, use an account with any crummy currency and not one from first-tier countries.