There are several things that drive the price of the Portland up:
1) It's a low-production model--not many units to spread the costs over.
2) The fork: Carbon, rides sweet yet it's stoutly built. Only carbon fork I'm aware of that has lowrider rack mounts. Used only on one other model, the LeMond Poprad Disk.
3) The frame: It's Trek's highest-level aluminum frame, and is unique to this model. It's noticeably lighter, yet better riding than my other aluminum Trek.
4) The wheelset: Disk hubs cost more, and these wheels are used on only one other model, the LeMond Poprad Disk
5) 105 drivetrain (with a splash of Ultegra) and levers. Mid-teens is about right for a 105/Ultegra bike.
My Portland was twice the price of my other Trek, and that's a bargain because to me, it's worth more than even that.