Don’t look at me. I had to look up what the hell that was. But apparently it’s not that hard to grow…
http://www.squidoo.com/arugula
Here’s my guess:
It’s a result of price descrimination.
In The Undercover Economist Tim Harford talks about how retailers utilize different item variations to maximize on price sensitivity. It’s actually pretty interesting. You can read it in chapter 2 here. And here’s an article where he focuses on the Starbucks example.
Just based off of what I’ve read, arugula sounds like it has a decently high snob factor, and is basically a substitute for lettuce. My guess is the higher price is a way for retailers to offer those who are willing to pay more for their lettuce products something more expensive to buy.