They're not. At all. The Optoma HD-25LV goes for under $1200 and does 1080p natively. I have its big brother, the HD-33 (1080p + 3d), and it's fantastic, especially considering that it was only $1700. Projectors have gotten really good and really cheap.

With projectors, lamp technology hasn't advanced all that much, so brightness is important, and is inverse with resolution.

quite a few 1080p under 1k. For example the excellent Benq w1070 ..