For various reasons of my own I want to buy the poster for Pop'n 15 AC (This one). I figure it's pretty unlikely anyone in the US would have a hold of something like this, but I figured it'd be worth a try before I try getting one through Rinkya or something. I don't know how much these are worth, so I'll base my decision around how much they go for on Rinkya (would be willing to pay more if I don't have to go through the hassle of signing up, figuring out how to work, etc.).
Will work out payment and stuff if someone offers.
Also, how do these things circulate in Japan? Do only arcade managers get them at first or are they distributed otherwise?
To answer one of your questions, AC posters and archbanners come with the upgrade kits. I don't know how people get them and sell them - my guess would be they buy/get the posters from the arcades or worse case scenario, steal them >_>
The best way to get AC stuff is to wait until a new version comes out. Then all the arcades that still have their will be selling them on yjapan.
Granted, a lot of arcades sell them right away, but then you'll have a lot of people competing for them and will have to pay more. (IIDX is far worse than Pop'n is, though)
Why not do a South Korean release instead. Japan is extremely xenophobic when it comes to video games. I bet Capcom had to tell the public that GTA is Scottish (or British for Stories games) and not American for it to sell. The South Koreans are much more open to American made games than the Japanese.