Your distinction between Breeder, Preservationist & chicken collector is a very useful way of putting things.
I fall in that middle group; preservationist.
I don't intend to have huge flocks or really go to shows w/ birds. I've got poultry at all b/c I'm trying to feed myself & DH from our homestead, I'm in that way an "end user" as I actually need exactly the traits of these older breeds, if my flock isn't foraging well and stops laying in bad weather we don't have eggs to eat, etc. But now that I have a little time in w/ keeping poultry on my land in my exact situation I feel that there is no point in my having random mutt birds. As long as I'm going to all this effort to have poultry I might as well actually contribute to help keep the gene pool of a rare breed (or a couple rare breeds) around. Given disasters like Katrina, Sandy etc. it is in the best interest of all that some GOOD birds be in many different locations. It would be hardly better than keeping my current mutts for me to have not really it (not to standard say) rare breed birds if the idea is my flock is a fallback for the gene pool in case of some disaster.
In my mind, to be doing any good as a Preservationist, I need to :
1) Start w/ the best stock I can afford, hopefully birds that are to the Standard
2) Make sure that I cull (eat) birds that are less perfect than what I start with
3) Bring in new stock often enough to avoid problems
4) Make sure that a few of my very best birds go back out into the wider gene pool from time to time, esp. to help others get started with the breed
5) Be willing, in the event of some terrible disaster to make my birds available to the true Breeders in the event they need to re-create lost lines / breeds of which I have survivors.
That is just how I personally view what it is that I am doing, what my aim is, why I'm willing to spend a little more than if I just stayed w/ my current mutts & hatchery birds.
I'm sure everyone has their own reasons and situation, but for me I feel like I can "do good" w/o having to become a top breeder, or attend shows, provided I do turn to the more knowledgeable Breeders for guidance on how well I am doing (or not doing) to keep my rare bird flock a viable and useful part of that breed's gene pool.
As far as the conversation re buying/selling culls - I think the term cull is very general in that it can mean anything from a sick bird that died & you burn it & its coop, to a bird that has an off for Standard color or something so you eat it, to the mutt birds I'm "culling" this week by giving to my neighbor who needs some chickens but wouldn't know a RIR from a Pheniox, to the jr roo Buckeye referenced earlier in this thread which would likely be far more perfect than anything I'll by from a hatchery but doesn't make the cut as best male bird for the Breeder who currently might cull that bird by selling him to a wanna be Preservationist like me.
FeyRaine