[PvK]

Supply is kinda weird in that it looks less efficient in terms of space than engines, and also in that it costs more than most weapons do. A tanker ship tends to be more expensive than a warship, at least before the final most expensive weapons are developed, and sometimes even then.

However those are not really balance issues. They are perception issues and "does it make sense" issues.

There is sort-of a balance issue in that it doesn't get you much to choose supply storage instead of engines, but since there is a max number of engines per design, it doesn't keep supply from being useful.

In fact, I suspect the reason supply components are as limited and expensive as they are, is an intentional balance design so that fleet range can only be extended at significant expense.

PvK