High Radon will affect the home price by about $1500. as that is a ball park remediation price. Once remediation is done, the Radon is not an issue.
So, it sounds if you are looking for a negotiation tool, $1500 is about it. Also, as I understand things in the area, South Brunswick and Somerset have a high level of radon gas in general compared to other areas.
Not a bad thing as this is a natural occurrence that just needs remediation.