I put burgers in 2 categories, simple and complex. Most times a perfect simple burger will rival the more complex, a lot has to do with context.
The best complex burger I've had is from Craigie On Main. It's $18, they have 18-20 available each day though some days you can't get it at all.
It's house ground with special beef and they add beef bone marrow I've heard.
It's worth $18 all day long.
Found this page while researching it
Burger/Bar Menu Rumor NOT True-Chef Tony Maws » Craigie On Main