On a plane?

> but $2 would be a more appropriate price tag for a few hours of Internet

Correct. That's (one of the reasons) why Starbucks coffee is pricier.

It also depends on where you are. Getting high-speed, low-latency internet to a shopping centre in the middle of a metropolitan area is probably a bit easier and cheaper than getting it to a plane flying 40000 feet above the Atlantic. And while I probably wouldn't pay $20 for eight hours of internet on a plane (unless I really needed it), I don't find the price tag entirely unjustified.