The build there looks good and tidy, and I would say it’s approaching competitive pricing if the shipping is not extreme. I really like the terminals and the secure packaging. But as an example of the challenges in judging build quality they have the cells on their sides, which manufacturers caution against. The electrolyte is liquid, so I can imagine why they don’t want it against a terminal. Maybe it needs to fit into a shelf system and that determines width. Do you need that shape? Given the option I’d pick upright cells.
DIY is still cheaper as well. The parts for a DIY 280AH prismatic battery setup with a MOSFET based bms like Daly or Heltec should cost around $1000 delivered, and will hold 7.2kWh, 50% more. Packaging may be another 100 for fancy, or 10 for plywood and tape. If you need 48v and have to buy 16 cells the parts cost goes up a few hundred since an capacity from a smaller cell costs more than from a larger cell.
DIY also requires assembly which takes meaningful time and effort, If you aren’t in the mood for that these packs are tempting. But shop around - I asked a question of one seller on Ali and didn’t get an answer to my question but did get about 10 inbound messages from other sellers. My Ali rule is that if I can live with things i don’t ask about being as cheap as possible it is an option, but if you know enough to shop smart you can probably DIY.