As others have mentioned, the EMP is not polymer. It has an anodized aluminum frame and steel slide and barrel. That costs some money. Springfield had to re-engineer the 1911 and the EMP uses something like 15 non-standard parts. This was done both to decrease size and increase reliability. As MLeake mentioned, the smaller guns are often more difficult to make reliable. The STI Shadow, Dan Wesson ECO, and most other small 1911s are actually bigger than the EMP. The STI LS is also very small and uses 1911 controls but is not a true 1911 since it uses a linkless barrel.
All in all, $1,100 for an EMP is not out of line. Obviously, however, you can buy small 9mms for much less. I have the Kahr CM9 at less than half the price of the EMP. Still, I sometimes think of getting one.