I am definitely a collector and decided long a go that whatever I collect (and I don't just collect cameras) should have a fairly tightly defined criteria. Within this criteria it is usually my aim to collect everything available, or as much as is economically feasible. If I know that something will just sit on the shelf then I am just as happy with a non-working example. If I have a choice at the time of purchase then I might spend a little more to get a better looking example of something, but if I already own it then I won't "upgrade" to nicer one. If it comes in multiple colours then I will buy all colours but generally draw the line at "collector's editions".
To give you an idea, I collect Pentax 6x7 bodies, lenses and accessories (and generally speaking draw the line at 500mm), Pentax MX and all accessories, the rest of the Pentax M and K series bodies (but not lenses) and Schneider Symmar lenses (but not the newer APO and APO-L lenses). The Pentax M and K bodies have been my bottom feeder moment with a lot of them being sub $20 bodies from KEH's as-is section and if I had to pay the usual price of a working body I probably wouldn't have bothered.