Well, I picked up a QL17 with flash and cases for both, instructions and camera strap, for about $50 US... clean enough to eat of off and in perfect working order. I understand that older machinery needs maintenance, and properly performed, it is well worth the price - however, the value of the original merchendise comes into play before the situation gets to a point of diminishing returns. I suppose it all depends on what value the item represents to the person - I have a 30 year old Zenit SLR that is of great sentimental value, and I know that the money I recently spent getting it working could buy me 10 of them... but I wanted my old camera fixed because it was worth it to me. Financially, it was a stupid move, but to me it was worth it. With the QL17's I found the range of shapes they come in is huge - from real wrecks to real gems - and the prices do not always reflect that (especially on eBay...)
I have heard that the meter on these cameras is at best... well... a helpful suggestion more than anything from people who have a lot of experience with these. My personal impression is ( and I might have just got lucky) that it is quite accurate and fairly sensitive when measured against various meters on my other cameras and those of friends (keeping in mind that meters do seem to have a bit of "personality" built into them even on pretty high end stuff)
My main concern with the Canonet 19 that I have is that the viewfinder is a bit dim - it appears to be an ease fix, but I want to make sure I learn about all the do's and don't's, just to avoid breaking or damaging something through ignorance.
Bottom line is - the Canonet line is a GREAT value, even if you do spend $100 on a good one, and real steal given that better deals come up frequently. I think many people who are not "into" photography end up selling them based on their unimposing appearance (they just don't look like a pro SLR with all the gadgets - therefore most "lay" persons don't realize the value of what they have on their hands!