[rickst29]

That allows me to do a "group buy" of 16 battery cells, reducing the proportion of expense spent in shipping (in comparison to buying only 4 cells at a time). It also allows me to turn my cell compression components and other stuff into more of a production line.

Cell compression, BMS, case, bus bar assembly, and terminals are the main reasons why battery "packs" cost more than individual cells. In some YouTube videos, you can see people "building batteries" by merely wrapping tape around the 4 cells and attaching the BMS -- that's not how it is done. These "prismatic" battery cells can last about 50% longer, if they are instead installed into a highly compressed, spring-loaded interior clamping structure. (The total pressure, sideways on these cells stacked next to each other, needs to be right around 240 lbs. It's spring-loaded because the cells expand and contract with heat and discharge current.)