I think they're operating on the level of people who are working to close deals worth 8-9 figures who know exactly where the 4 decision makers they're targeting are going to be at 8:30AM and 5:30PM. There's not much more to it than that; the only real observation to make here is "these deals are worth a lot of money".

I've priced doing billboards just for funsies --- to make a (snarky) point, not to make money. It's not that expensive! Also: how could it be? Look at some of the terrible billboards out there. There are a series of I-55 billboards advertising a single self-published book of poetry.

Your original statement was "normal humans don't try to communicate directly with each other through the media". I think you're using a pretty idiosyncratic definition of "normal" there. The phenomenon you're labeling abnormal is I think actually pretty common.