That looks quite a bit cheaper than the pricing I'm used to seeing, like less than half - not saying they're bad, but probably there's a DIY and risk factor involved compared to buying a more established brand like BYD or Huawei.
I'm just pointing out this is way lower than typical pricing
Maybe, but I think the premium charged by the main manufacturer's is unjustifiably high. Those battery boxes are relatively dumb: besides the cells, they just need some voltage and temperature sensors for monitoring, some power electronics for balancing, a microprocessor, and an enclosure with connectors. Unlike a grid-tied inverter, this is a really simple system, and there's no way a 500–700% price premium over the cells is reasonable.
I'm just pointing out this is way lower than typical pricing