40-50% price differentials in the same metro area: that's the very textbook definition of inefficiency.

You must have a really bad textbook. There's vastly more than a 40-50% price differential in the cost of getting a dinner at an Italian restaurant in my metro area as well. Does that mean the restaurant market is inefficient? Or perhaps it's because the characteristics of an Italian dinner vary wildly across different restaurants.

Or heck, we don't even need to get into that. A quick google search reveals that the cheapest price of gasoline in Miami right now is about $2.72 per gallon, while the most expensive gasoline is $4.39 per gallon. By coincidence, pretty close to the same range you note in your excerpt. I guess the market for gasoline (a purely fungible good whose prices are perhaps the most visibly advertised of any product that exists on the market) is a textbook definition of inefficiency....