The ad-blocker won't load the ad at all for two reasons. 1) Performance. Less to load (and process, and render, etc) means faster load times, less bandwidth consumption, lower CPU usage (think about all those extra scripts), etc. 2) Privacy. If your computer contacts the ad network at all, then it could track you.

Because the blocker fundamentally can't load the ad or contact the respective network while also doing its job, triggering a payment would seem to be more or less impossible.

Not at all. Most of the industry moved away from CPC a while ago due to how dodgy it skews data. Most clicks end up being bots on shady websites Vs actual people. Viewabilty is what the good agencies are advertising against now; with the hope that you'll navigate to the advertiser's site down the line.