I am talking about large corporations like JPMorgan Chase (the subject of the article) that are on the internet, tv, radio, billboards, print, sponsoring conferences, sports teams, lobbying governments, thousands of physical locations and ATMs that people see every day, etc, etc, etc.

Even with a PPC ad that results in a conversion can you really attribute that sale to that particular ad?

For a large corporation no, because you can't tell what part of the sale is due to the corporation's existing brand that is built up through exposing the consumer to that brand thousands of times across multiple media.

Conversion rates for digital ads are only meaningful relative to the conversion rates for other digital ads. They do not not allow you to attribute a value to digital advertising relative to the rest of your ad spending.