I don't think the original game devs playtested storage very much, or even at all really. The numbers are positively ridiculous. If you were to take a 3D render of the comically small representation of the facility itself from the battlescape and fill it with life-size renders of 50 space units of stuff, it would just be scattered across the floor and wouldn't come close to filling it. But if you ignore realism and go by just gameplay alone, the bare-bones starting items already more than fill your initial general stores. The only reason you had a tiny bit of space left over at the start of the game was because the game didn't count space for the items loaded onto the crafts. The remaining space was about big enough to buy extra ammo and smoke grenades, maybe some electro-flares. But you couldn't actually spend your money and buy the stuff you needed until 10 days went by and your second general stores finally finished. And if you're a veteran player, probably your third and fourth as well.
One of the most annoyingly space-draining items is the 1.5 space avalanche missile. To purchase 4 launchers for your 2 interceptors, with enough ammo to load them and have one spare rack, it costs 40 space units. That's 80% of a general stores just to barely load out your interceptors. But it's not like the avalanche missiles take up too much space. Compared to everything else, the space they take up actually makes sense when you consider how big they are. What doesn't make sense is that apparently the entire available space in your stores can fit against one wall.
It would have been completely reasonable if they had moved the decimal point over and shifted the size of each item down an order of magnitude.
