Yeah that's pricey. I think my Acura dealer probably charged upwards of $450 for the installation: I thought the price was supposed to be $449 installed, but at sale time, it became $499, and I doubt the remote was more than $50 (well, maybe the transponder (? - what simulates the key being present) could be another $50).
You might try to negotiate with the repair shop manager. Unlike almost all other work, which has known hourly times associated with them, I doubt there's anything in concrete for a remote starter installation. If you can find some quotes from local installers, you might say, "They average around $325 for installation, how about you do it for $475?" That's still a decent profit for them, especially if the alternative is to lose a $600 sale.
Also, in terms of remote starter features, some of them have buttons for 'auxiliary channels', basically remote switches. You make consider one of these so that you could have it hooked up to the defroster switch(es), that way you can turn them on remotely as well.
Jeff