I guess traffic gets a lot cheaper beyond a certain volume. I suspect it's dollars/TB to cents/TB? So they can cut prices for their offerings and have more revenue and growth due to paying less for the traffic. Having these volumes of data also allows them to approach potential clients with some solid data (e.g. we serve 1/5 of image clicks on the net every day and below 20ms response time... I have no data, just speculation)

I could imagine that imgur traffic paid for itself.

So I should start a burger joint and give away food for free to prove I can handle the throughout and my cost will be essentially zero?

If you have robots in the entire supply chain down to the production of the fertiliser for the plants without any humans then why the hell not?

Burgers are not bits.