You're right around fair value at $600. Civilian versions go for around $300.

By the way, this is the only gun I've owned thus far that can actually be taken apart wrong. TRUST ME. If you do take it apart, there is a very specific way to do so. If you do it wrong you'll spend HOURS trying to jiggle all the little bits out of the receiver to get it apart.
I read an account of someone that gave up and had a machinist cut the slide away to get his apart.