I would like more info before I take a swag at a price. Like the age of the gun (the dash # would help, or the first part of the serial #). Also, if it truly is NIB, is this a private transaction or an FFL? Noting that you are in Illinois, and subject to somewhat different requirements than some of us, this might tend to drive the price up. And I am assuming that porivate sales are ok there given IL law, which I'm not familiar with.
You can check the S&W forum, though, as those guys might be a better resource.
OTOH, good 95% plus Model 19's can go from just under $300 to $400 or more, depending on the local market and real condition, plus the luck factor. I would expect a NIB gun to be at the higher end of the market in any location, but that's a no-brainer. Especially from an FFL.