[MichaelMcG]

Exactly, this appears effective projecting the fixed budget for one specific tactic, on a product with geo or demo targeting limitations.

The blog post failed to mention that when scaled up there is much more in play than strictly consumer acquisition (e.g. brand awareness) that is just as important when marketing in most B2C verticals.

[mektrik]

You're right that there's more than just last-click cost per conversion, but that doesn't mean this approach is incompatible with these extra complexities.

You might run conversion lift tests as a way to calculate the impact of increased brand awareness, and you could plug the data from these into the method outlined in the post. There you'd be looking for the optimal cost per incremental conversion rather than just optimal cost per conversion.

This is just one idea, hopefully shows that the post's method doesn't have to just use last-click conversion data.