The funny thing is that if you asked people how much caffeine is in a cup of coffee vs a can of redbull I'd bet a lot of people would say the redbull. But a single cup of coffee actually has, on average, maybe twice as much caffeine. People don't realize how much caffeine coffee has, it's a ridiculous amount. Pretty much the only beverages you can get at starbucks that has significantly less caffeine than an 8oz redbull are the teas, hot chocolate, smoothies, and decaf.
I think people underestimate even more the amount of caffeine in green tea. Some kind of green teas, especially the like of Kabusecha/Gyokuro, have way more caffeine than coffee. Up to three times as much in a cup of tea than in an expresso in the case of Gyokuro...
