I think if I was on the market for another 600, I would offer somewhere between $300 and $400. The fact that it is chambered in one of the less desirable cartridges (from a collectability standpoint) means that it would compete with many other mass produced rifles. However, if you find someone who really wants a Model 600, you may get a little more. The cracked trigger guard is going to be an issue, however.
The two chamberings that I see bringing higher than average prices are 308 Win and 350 Rem Mag. I did see a 6.5 Rem Mag version go for $650 a couple of years ago, but it was like new. The 223 version is the rarest; I have never even seen one.
Questions about 7.62 NATO and 308 Winchester? Click here