>>3140753950 euro does seem like a lot for that, however buying full outfits is definitely the way to go. I paid $850 australian for my rb kit, but it has a lot more lenses, and better ones.
I'd say if you can inspect the kit first, and it's literally pristine, AND you really want to shoot with an RZ a lot, then whatever, it's just money.
However, don't sell the prism finder, especially if it's a light-meter model. TTL metering is absolutely invaluable with a bellows-focusing, half-stop max aperture abortion like the RB/RZ series. Also being able to see the viewfinder in sunlight, or if you want to shoot at eye-level is pretty useful.
If selling off the other body, I'd recommend picking up a 127mm and 140mm, shooting with both, and selling the body with whichever one you like less.
Regarding backs; motorised backs a best, keep them. 220 backs are good, but you will only ever need one in 2017, as the odds of you having 220 stock of more than one type at a time are pretty slim. 645, 6x6 and 6x8 backs are collectible, keep them. If you can fling a basic 120 and 220 back and still have plenty for yourself, you're golden.
Also, shoot with the 250 and determine if you really need it, and maybe add that to the sell-off kit. It's a bit of a boat anchor, and the choice between taking it or another 2L of water on your next hike becomes a lot easier if you've just sold the fucking thing.
