This mod has great designs but bad balancing. The material costs, storage capacity, and usable cells don't make any sense with each other. For example, the barrels have an abysmal capacity for how much it takes to make them. I'll open a discussion with this as the topic if you want to chime in and suggest balance changes.

I am aware that there is another mod that balances deep storage units, but it would also be nice if Simple Storage were to try and fix it themselves, because that mod is currently unmaintained.