> there's a pretty fair chance that the advertiser has done that math
As an occasional admittedly naive experimenter with ads – it’s far more likely that the platform has done the math and showing you the ad is profitable to them, not the advertiser.
Google et al love nothing more than to burn your entire ad budget on cheap clicks from countries that will never buy anything. But the number of “ad conversions” looks high and graph go up!
Getting these platforms to do what you want is a literal full-time job. Hell, in bigger companies you have entire teams doing nothing more than bending over backwards to get these platforms to do the useful thing instead of setting money on fire. The algorithms love setting money on fire. It’s a lot like giving your 3 wishes to a genie, you have to be very specific.