Why Starbucks Prices Went Up as Coffee Beans Got Cheaper – The New York Times:

“‘mobile payments now represent 20 percent of all in-store transactions in our U.S. stores, more than double the figure from only two years ago.’ I use an iPhone app to pay these days: It’s easy to transfer money without noticing the cost.

*The cost disconnect for customers who don’t pay with cash. This leads to less price sensitivity.