I sold mine long time ago and was not regretting it. It is a closed system, I have 2 bodies and all lense sold when the price was good. I don't see the reason to keep the glass, unless someone wants to convert the Mamiya 7 to accept digital back. A friend of mine bought the Mamiya 6 version and adapt to use with digital back that works very well, a really nice compact system that is.
But there are many ways to shoot photographs as there are many cameras, I will try to master the tools I have, I couldn't have everything.
To collect, Mamiya 7 is not on my list.
Pingang
Shanghai