Is $9,000 to install rigid foam insulation a fair price?

I hired a siding company to install Hardie siding. The project manager offered this quote for rigid foam insulation as an add-on. I'm questioning the effectiveness of R-value 2.5 and if it's worth the $9K price tag, especially since my area doesn't see temperatures below 0 degrees Fahrenheit. I'm also wondering if it will help with drafts, but the house is already being wrapped for the siding process.