This has been a great discussion to read, if a bit late. I'll add a couple of data points that may prove helpful--the stuff at the end is probably way more helpful than the early bits.
First, I started with an RB67 which I bought as a kit from KEH back when they could be picked up *stupid* cheap (about 2010, if I recall correctly); I chose it for the fact it was a mechanical camera, and it and the lenses could be repaired by a competent repair person. And did I mention that it was crazy, stupid cheap? I took it to London with me (I lived there for 10 years). I used to use it frequently in the studio, and built a nice, fairly complete kit over time.
I later traded it in on a Hasselblad kit when one became available at my favourite South London camera shop (
http://www.croydonphotocentre.co.uk) as I rarely took the RB67 out of the studio, and I wanted a camera I could use indoors and out. And it was a *Hasselblad*! I didn't regret that honestly, and still use that gear constantly.
Later, I came into possession of an RZ67 Pro II and a couple of lenses (the 127 and 140 macro) & backs for next to nothing. (I was at the annual Photographica event in May of 2014 in London, and the guys from Aperture--where I was a regular at the Camera Cafe--had a table set up. When I stopped to chat, after a bit one of them pulled a bag out from under the table and said, "Here, buy this from us, we want to go home!" It was the aforementioned kit. I asked what they wanted for it, and he was like, "Ah, just give us £400, mate, and it's yours." Sold!) I used that in my studio not only to shoot film, but I found a cheap Sinarback 54M digital back with RZ adapter, so I *mostly* shot digital with it. If you want to see what the 180 W-N lens can do with a 22 megapixel digital back, go here:
http://www.presquevu.com/apa071.jpg. I added on to that kit, too, and eventually had a very nice setup.
Unfortunately, in 2016 I had to move back to the US due to my father's illness--he was going to need my help for a while. I had to sell off a bunch of stuff to raise money for the move, and I had to make a decision on my medium format kit. I elected to keep the Hasselblad stuff, as again, I could use it indoors and on the street. So I sold all the RZ67 gear and the digital back. Got a good price for it which paid a big chunk of my relocation expenses, but *damn* was I sad to let that go! I'd definitely fallen in love with it.
Fast forward to last week. I decided I would use my stimulus check (Thanks Joe and Nancy!) to replace my mourned RZ67 kit. Unfortunately, prices--as all here have observed--have jumped hugely. I was determined to keep the price of the whole kit under $1400 if at all possible. And I've managed to do so, to this point, with some room to spare. So here comes the more germane bit.
First, KEH had an RZ67 Pro (not a II unfortunately--those are kind of ridiculous at present, when they're not a whole heap better than the original version). It was $412, without a WL finder and with no other accessories, in BGN condition. I grabbed it--I've seen that almost as soon as an RZ body shows up at KEH, it goes--and when it arrived, it was in very good condition. Obviously used, but definitely not ragged out--waaaay better than some described as Near Mint on eBay. I also snagged an Excellent condition 220 Pro II back at the same time for $35 (I have loads of 220 film in the freezer still). The back actually had a scratch on top of it, but it was indeed in great shape otherwise. So I felt I got a great score from Old Reliable, keh.com.
The 120 Pro II back was more expensive--I wanted to stay with Pro II backs for the light seal issue--and that cost me about $188 including shipping (about four days in transit) for one from a Japanese eBay seller. Advertised in Mint condition, it was. (As others have recommended, *carefully* read descriptions from Japanese sellers.) I also bought a 140mm M/L-A Macro (love that lens) from another Japanese seller. Advertised in Mint condition cosmetically with a bit of haze, I watched it on eBay where it was listed for $189 plus $40 shipping. The seller almost immediately offered it to me for $149, and I took it. It also arrived very quickly--most Japanese sellers use DHL--and was in exactly the condition described. The haze isn't so bad as to be unusable, and I'm pretty sure I can clean it when I get a set of Japan Hobby Tools rubber lens tools, which are on order.
I got another 180 W-N on eBay; this came from a Taiwanese seller, Shueido on the 'bay. He has lots of Mamiya stuff for sale, and I can highly recommend the seller. I bought a Hasselblad 553ELX from him for $400 a few months back which looked brand new on arrival (it turned out to have a small, but not immediately notable, mechanical problem; he offered to take it back for repair or give a $100 refund; I took the refund and had Hasselblad USA sort out the problem and give the camera a CLA, which it probably needed anyway). He advertised a cosmetically very nice lens which he said had been CLAed and had pristine glass, for $109 plus shipping. I offered $90 and he accepted it. The lens did have a blemish or two on the outside, but the glass was as good as advertised. Again, very fast DHL shipping.
I got a very nice WL finder off eBay from Wings Camera in Atlanta, where I'd bought loads of stuff in-store when I lived in the ATL. I didn't bother bidding, did the Buy It Now option, $128 including shipping. And I've got two extension tubes (#1 for $44 from a Japanese seller--regretfully, I later found another seller offering it cheaper--and #2 for $19 from the US) and a Polaroid back--I still have *five* boxes of FP100C in the fridge--from another US seller on eBay for under $40 including shipping.
Unfortunately, the other two lenses I've got my eye on to give me a good spread of focal lengths are *really* expensive right now. I'm wanting the 90mm as my "normal" lens, but it's silly costly, and the 50mm (non-ULD) is not so bad, but still pretty expensive. I'll have to wait on those.
So, if you don't mind (1) keeping your eyes constantly open, (2) buying from international sellers, and (3) assembling your own kit from a variety of sources instead of buying it all in one go--full kits seem to sell for a significant premium--it's *possible* to assemble a reasonably priced kit for portraiture and closeups at least.