I believe the provenance is what bumps up the value. I would be shocked if it actually sells for over $15,000. Unless there are two or three people in this world that are willing to pay tens of thousands for that provenance. Who knows, the author may have knowledge that there are, in fact, several wealthy people who want it.
Nazi-marked Mauser Lugers go for more than Erfurt-made ones. Provenance is everything to a lot of collectors.