This is new to me, even though I have been on this board from the very beginning. Collecting, that is. I have always been into the technical side of it all, not the collecting side.
But, that seems to be changing.
As I went looking for a DSLR for my wife, and not wanting to spend a lot until I see how she takes to this new hobby, I find a lot of useful 'what was once high, now low' out there. Stuff for under $200 all over that was once $5000. I bought her a $60 D1H and the thing works just fine. OK, too large and heavy for her. I use the old Kodak 7xx series still, so I think of a D1H as small and light.

OK, I got her a D80 with two lenses for just a bit over $200. So, she is off and running and getting used to that. Then, too, my one Kodak battery charger crapped a cap(acitor) a year ago and I have been charging my one battery via my lab bench power supply method. That works, but leads to only about 2/3 of a charge so I don't detonate the battery. Now, she wants to take 'photo trips'. Now I need at least one more battery and another proper charger.
I went looking, and picked up a cheap Kodak 520. Yeah, 2 MP, and Canon based, and this is a Nikon site. But, the battery charger was there and a spare studio supply, and two batteries. Which show half capacity each on the first cycle. Useable, and might improve with repeated cycles. But, now I have another DSLR I seem to have collected. Oh, well, maybe I'll use it for eBay shots. It does mount my Nikkor AI lenses with the adapter I have. Plus, I also have a microscope mount for my lab scope that fits Canon.
So, now I am up to four (Kodak 720x, 760C, 520 and D1H). See, for me, I may as well keep the two recent ones as they are not worth selling vs a possible useage.
Does this make me a budding collector? Maybe.....

But, wait. There's more.
I see where the D2 series seem to go for around $300. And there are some posts here pointing to the D2X as the most useful of the collectables. Then, I see where the D3S goes in the $700 range and it is full frame. I keep eyeballing the Df, as that is what I wanted in the first danged place back in the mid 90's. But, the D3 and newer aren't on the collectible list from what I can see.
Is it just time that determines collectibility? I had thought it was turns of the development crank. But, then for me, those turns have always been a factor. I am a developer of such things, and after two turns of the crank I call things 'vintage'. But, that doesn't seem to work in this case or you'd all be on about the D3 series.

I will probably get a Df sooner rather than later. There is a tie between it and my old film cameras and the set of lenses I have kept all these years. Yes, they work on the 'F5D' and would work on a D2 and a D3. But, they will only look right on a Df.

But, I sit here now thinking I ought to add a D2X and a D3S to the 'collection'. And, dang! I let all my E-series units go long ago. Well, not that I would ever use an E-series again. But, for a Nikon DSLR collection I should have kept at least the one where the power switch / shutter button fell out of.
The bottom line is: what do y'all think when it comes to Collectible?
Stan