Nice, you found a NTSC cart of Conker in Japan for around 100/050 yen? Now I'm tempted to go N64 game hunting when I visit Tokyo in July. Any advice?
No no, Sorry. Those bottom four games are from the US. Perfect Dark and Conker from my original N64 collection, and Chameleon Twist and Clay Fighters I snagged from a customer while working at Game Crazy.
Hm. Well going to Tokyo, you're probably not going to find the best deals easily.
Just check out every game store you can and don't be afraid to browse through the bins that are clearly marked as 'junk'. Honestly I can't think of a single game I got in the junk section that didn't work with a good cleaning. They'll probably be boxless though.
The 50yen games were marked as such at GEO stores (game purchase and movie rental store chain) when they were getting rid of their older game stocks. By the time I moved there, they were already in the process of liquidating stock, I think. Everything was marked 105 yen.. eventually I found them marking the left overs at 50yen. Crazy good if you could find a decent game in the mess.
The bigger game stores will have the best game variety, but the worst deals.
If you want deals, you'll want to hit junk stores like 'Hard Off'. Here they are scattered around the Tokyo area:
https://www.google.com/maps/search/hard+off/@35.7095757,139.6863774,11z
Street view them to get a good look. You'll see those blue and yellow signs as a glorious beacon for junk games. Don't be discouraged if you find nothing. You'll comb through piles and piles of baseball and pachinko games and often find nothing.
I'd also recommend a quick visit into miscellaneous Recycle Shops. Often, mom and pop style shops don't know what they're holding onto.. You just have to get lucky, and be at the right place at the right time.
If all else fails, no joke, Amazon Japan. Just search for a game you might be looking for, and buy it used from a low priced seller. I ended up rounding off my Famicom collection by buying a lot of the games I couldn't find, straight from Amazon Japan. The prices here are almost always cheaper than I could find them in the big game stores, and there was only one game I ever ordered at 'acceptable' quality that looked awful. It still cleaned up pretty good.
Almost every game in my collection is from a Hardoff, honestly. You'll love the song they play in the store once it's drilled into your head. Doo do do do!... Dooo do do dooo... dooo! Anyway, just check everywhere you can, and again, the junk sections are where you wanna be. The only junk items that usually don't work will be painfully clear in that regard, and junk consoles will actually be marked concerning whether they've been tested and what the problems are. I'd often buy the untested ones, just because they'd more often than not work, anyway.
Good luck!