I live in Tokyo, and I've seen tons of similar-looking arcades close within the last 10 years I've been here, including some in very recent years. Video arcades are still somewhat of a thing here in Japan, unlike most other countries - though they are rapidly disappearing here as well. As others have pointed out, judging by some of the games pictured, this arcade hasn't been closed for more than maybe 10-15 years at the very most, and I'll bet it's actually a lot less than that.
I should mention that I do collect arcade boards a bit myself, so I have an idea of what the market is like here in Tokyo. To put it bluntly, the majority of this is considered junk here - especially the cabinets, which all have CRT displays. CRT cabinets are desirable to classic arcade game collectors - maybe to have just one or two at home for personal use - but the majority of them get hauled to the dump nowadays since there is little demand for large quantities of them in still-operating arcades. As for the boards, I'm sure there might be a few semi-rare ones in there that might sell for a few hundred dollars, but I can tell you with certainty that most of them would likely sell for the equivalent of $5-30 US$ in an online auction in Japan. To be blunt, the reason this stuff is still in this building is because the previous occupants didn't have the money to have it hauled to the dump - and little of it has higher value than it did when the arcade was closed. Most of it has probably actually gone down in value.
This is really a poor excuse for news, and I'm surprised Slashdot bothered posting it. It might look like a cool find to people outside of Japan and people who don't know much about arcade equipment, but to those who do know, this find is barely worth mentioning at all. I would consider it a pretty cool find if a friend had found it, for instance, but it's certainly not international news-worthy.