In EU anything below 1000€ is either a very old Leaf that requires some weird cables, or old Phase One backs that can only be shot tethered. While someone in the studio might be fine with that, they will also end up with something that costs quite a bit as a complete system (back + body + lenses + Mac) and that still has a 24x36mm sensor (or a weird 36x36mm).
Imacon backs start from 1400€ for the back alone in H mount (which means spending 2000€ to 4000€ more for body+lens in good conditions), or a complete V system with a 150mm Sonnar. All Imacon solutions are based on the Imagebank (or can be tethered directly to a Mac), which grounds them in the studio. At least those have sensors bigger than 35mm cameras.
Anything more modern than that, and you're looking at spending something between 4500€ and 8000€ (without going to the various IQ/Credo and H5D stuff), at which point you are much better off paying a bit more and getting something new OR investing all that money in a complete 35mm system with two bodies.
Prices on the used market haven't changed much from last year and they look less and less interesting as very old stuff is being sold at quite high prices. Leica S is even worse than that, as it loses value slowly and the difference between used and new prices isn't that much to even bother. Pentax used is pretty much just the 645D, if you can even find one. But good luck with the lenses.
Then there is the odd Mamiya branded DM or ZD back, which may come in wildly differing prices because some people don't seem to have a clue what the value should be. Oh, and the rarest of them all, a Kodak back! I've only ever seen one and it was gone in a few minutes, but it's not like you have that much choice.
Probably the best of them all has to be finding a good H3D kit. You will be stuck with an old back, but it will have at least a better screen than the H2D or H101 solutions.
