There's some very significant additional costs of bus bars & holding racks, but holy heck man EVE LF280K batteries are amazing. Usually 300Ah cells/<$90. That's basically 1kWh of energy (~3.2V average ish).

Building a big 14s 14kWh serial pack is really not hard, albeit those small hardware costs (bus bars) can add up. Most people don't need that much energy, probably, but these cells are just epic, maybe go 24v if you want less. 8k cycle life makes them good for a much much much longer time than most cells.