Yes, we needn't get bogged down in numbers, all we need to know is that with rarity set to 'Standard' it reflects the fact that in the real world, hard-to-get items cost more.
For example I've just begun a Tiny QB against Grober with Standard rarity, and could only have afforded 1x T-90(APS), so I decided to buy 4x cheaper T-72's instead..:)
PS- this panel (below) in the top left of the purchase screen also takes some figuring out; I can understand the one on the left, but the Standard rarity one has got me scratching my head. But no problem, like I said all we need to know is that rare stuff costs more without going into the maths, and that's good enough for me..:)