Really? I owned the 17-55. It was overpriced for what it provided. The 18-135 STM is a bargain and, if you can live without the 2.8, is a better choice for most people.
The f/2.8 constant aperture is the main reason it's so expensive. Wide aperture zooms don't come cheap, and many do not include IS which this lens does. What did you not like about it that made this lens overpriced?