That rare NES cart lot pic at the end is drool-worthy. I'd do some crazy things for a copy of Little Samson or Snow Bros. How were the majority of those acquired? Locally? Online? Specifically Little Samson, and Snow Bros.
Many of the harder to find NES carts I bought online either through ebay or nintendoage. Only a small few did I find locally for super cheap. I bought nearly all of them in semi-unusual circumstances which at the time meant that I got them for less then they were selling for regularly. And I bought them all long enough ago now, before many of them had price spikes, that the prices I paid are basically a steal these days.
For example with that Snow Bros I bought it off Ebay. This pics and description showed that someone had filled the screw holes on the back of the cart with some kind of goop most likely in order to avoid swapping the board out. I dont know who would do that besides a rental store, but there were no rental stickers on it so it was a bit odd. The price was a bit lower than most other SB at the time so I took a chance on it. I was able to use a small screwdriver and simply pop the crap out of the screw holes VERY easily and had myself a nice looking cart!
Little Samson was a bit less interesting though. Treated myself to a B-day gift a few years back and paid typical online prices for the time.
Some of the other more interesting circumstances were:
Bonk's Adventure - ebay (No pic and low BIN)
Chip n Dale 2 & Duck Tales 2 - nintendoage (bought together when seller needed quick cash)
Die Hard - nintendoage (received as a secret santa gift)
Dragon Warrior IV - Pawn Shop (third one I've found locally for less than $5)
Gun Nac - ebay (bought from seller who wouldn't ship to Canada. Had him send it to Duke.Togo and then he eventually sent it my way)
Bubble Bobble 2 - ebay (no pics, low BIN)
Romance of the Three Kingdoms II - Craigslist (wasnt a game collector, just a guy show LOVED RotTK. Said he had finally moved onto RotTK VI, lol)
TMNT Tournament Fighters - ebay (most recently purchase, very low BIN that I snagged within a very short time of its listing)
Zombie Nation - ebay (no pics, low BIN)
Gemfire, Godzilla 2, Pro Sports Hockey, Jetsons - nintendoage (all from one seller plus other goodies like DK Jr Math and Color a Dinosaur)
Stadium Events - ebay (very poorly listed, by very shady seller. Won auction for significantly less than last 2 sales on nintendoage)