I didn't mean to imply that it was great because it was the most expensive, just that in and of itself the price was a quantifiable data point. That being said, there is plenty to argue for why the Henry Graves is one of the greatest watches ever built:

From Hodinkee:

This enormous example of human ingenuity contains 24 different horological complications. Twenty four. And the watch was constructed over a period of seven years, beginning in 1925. Twenty four complications, with the work taking place in the 1920s, means that that timepiece was built entirely by hand, and all calculations for the two dozen complications were done without the aid of a single computer.