For my league my bleachers pricers are not high, most everyone here has higher prices, including my key rivals who regularly have been selling more, at a higher price.
We (the US offsite group) have a tool for calculating attendance/prices to optimize arenas. It's based on US data, so there could be differences between countries, but for us, it's very accurate. Based on your arena and prices, and assuming you're doing well in d1, here's what I'd expect your attendances to be:
Bleachers @ $19: mean 13k, range 11k-16k, with 16k only for top teams coming off a win.
Lower tier @ $44: ~3500, at most 3700.
Courtside @ $177: 450-470
Lux box @ $888: ~45.
The data these are based on was collected in previous seasons, and you seem to be right in line with them, so I don't think I see anything obvious to suggest that there's really anything different this season. The only thing that seems even borderline is that your bleachers are at the bottom end of the spectrum, but that's pretty typical after losing the previous game, and could be a difference between US and Japan leagues. Now, if you want to argue that the variance on bleachers depends too much on the previous (usually road) game, I'm right there with you, but I don't see anything really convincing that something has changed relative to previous seasons.