That's an interesting point, and I definitely think that sponsoring an event attended by your target audience is a big step up from TV or billboards.

Now this gets heady: "People are willing to pay a premium for things they can track." Perhaps advertising vectors which are easily tracked, thus optimized, yield more valuable per dollar spent. If this is the case, demand for this inventory (Adwords, etc) increases. You would expect it to become more expensive by forces of the market. This is why you don't see people lined up to fill billboard inventory, especially in the last 10 years.

It is a chicken-egg problem in some ways, but I think people are willing to pay more because their advertising/conversion math enables it, and that math is easier to back up with facts.