jmpTT
859
Not too many data points...
With only 11 ever made, the secondary market price is going to be volatile, similar to anything that changes hands very infrequently. This exact watch may not come up for sale in the secondary market for many years or there may be a motivated seller already (unlikely). Sapphire cases are uncommon and wear quite a bit differently, so you have to trust your own preference.
It's an absolutely spectacular watch in all case shapes, materials and sizes though. It's a very small community of owners, and we're lucky to have a few here.
If you haven't already and value retention is on your mind, I'd suggest reaching out to Steve Hallock. He resells on this site (as well as his own) and he also seems to be a Greubel Forsey enthusiast.