to do it right is a big job, if the inner arches are rotten up to the suspension towers then its going to be big rebuild job. 6k maybe there or there abouts as it gonna need taking back to the bare shell, rust cutout, new steel welded in, then built up, before being sprayed. im assumming the full respray is a full strip and respray, glass out, interior out etc etc, short version, its a duck tonne of work hours to do it as i bet they have priced it based on finding alot more like sills and such needing to be done as well.