Not to get to far off topic, but I think the 1st party Hasselblad V to Mamiya 645 adapter has existed for a long time? The 500mm APO Rollei lens is I believe is the same as the Hasselblad version, I could be wrong though comparing the diagrams:
Medium telephoto prime lens. Announced: 1982. Production status: Discontinued. Maximum format: Medium format 6x6. Mount: Hasselblad V. Slow speed. Internal focusing (IF). Built-in leaf shutter. Manual focus only. Automatic diaphragm. Heavy. Compatible with teleconverters.
lens-db.com
Medium telephoto prime lens. Announced: February 1999. Production status: Discontinued. Maximum format: Medium format 6x6. Mount: Rolleiflex SLX. Slow speed. Internal focusing (IF). Built-in leaf shutter. Manual focus only. Automatic diaphragm. Heavy. Built-in telescopic lens hood.
lens-db.com
The Hasselblad version is only ~900USD used :
https://www.keh.com/shop/hasselblad...ns-for-hasselblad-500-series-v-system-93.html
From rolleiflex.us: "Zeiss did make a very rare 500mm Tele-APO-tessar version with improved optics, but rumor is that there are only about 100 copies or less made." :/
Not even collectors, just anyone who wanted a good long lens for the 6000/HY6 series. I'm not sure why anyone would do this, the Rollei lens has to have been more expensive than the V version at any point....Even if they had it already, they could have made wayyyy more money selling it and getting the V version.