Yeah, when you say "rust free" typically means just a little surface rust. I've never seen an XJ of that vintage completely rust free. Look very carefully at the underbody, under the carpet, at the body joints and inner fenders. A small rust bubble could be a major can of worms especially around and under the fender flares.
Trust me, I've been there, and it ain't pretty. Rust never sleeps!
That being said, mines full of new parts, floor pans, full interior, heat/air system, new paint, complete front end, tires and wheels and much more.
I'm asking $5500.00 so at $4500.00 it sounds reasonable. Also pricing has a lot to do with location, location location.