Yeah, I have followed Amazon JP for a while, I guess it isnt very accurate because of wide retail presence of both Platforms and the popularity of the Nintendo online store in Japan. The 3DS for example always regularly beat the PS4 despite being generally behind it on Amazon JP.
It does show when there are boosts though, so the PS4 should sell better next week but I doubt any boost will be enough to overtake or even get very close to the switch. I still thimk there will be at the least a 10k difference.