Way too high. Should be more in the 300-400 range.
600$ is too high especially with a mismatched magazine. I would say 300-500$ in todays climate (K11s don't have the same appeal that K31s have). I can't overstate how much a mismatched magazine hurts the value of a Swiss rifle, as they are mostly all matching.
I got one all matching a month ago from csc for 315 bucks, but it was the last one.
Not lucky. Lucky was the guy that bought 5 of them before me.