In an investor presentation released Wednesday, Shake Shack touted its first "cashless shack" - located at the company's Astor Place location - which opened in New York back in October. As we pointed out last year, self-order kiosks have already become a staple at thousands of McDonald's restaurants, and Shake Shack is rapidly catching up. As a result, the company says it has been testing the sleek-looking kiosks at six restaurants.

And here things got confusing: people are Shake Shack's "most valuable asset" - the crucial component to the company's theory of "enlightened hospitality," it said in its presentation. And yet, by "valuable" it turns out the company actually meant "expensive" thanks to to rising rising cost of unskilled labor - thanks to movements like the fight for $15, which has pushed several large US cities to raise the municipal minimum wage, in some cases all the way to $15.