system
Given the following post, respond as if you're commenting on Reddit:
human
[Zootopia] How does currency work across the different districts?

In the film we see a town for small mammals, and at Mr. Big's daughter's wedding, there is tiny cakes for everyone. Obviously these cakes only require a tiny bit of ingredients to make, so they must not be very expensive, but do the small mammals make less money, or are they all outrageously wealthy proportionally to the rest of the city?
gpt
If they're all roughly equal in cognitive capacity, you'd expect small mammals to gravitate toward white-collar work where their size disadvantage is less of a problem. A mouse programmer is presumably just as effective as a giraffe programmer, and mice have much lower expenses, so yeah, you'd expect them to become tremendously wealthy.

The only possible advantage that (some) larger animals have is longevity - more time for individuals to acquire skills and connections in their field. You'd expect successful smaller animals to be very conservative, communitarian, and tribal - amassing connections and wealth and knowledge as a group, across generations, rather than individually. And since that conflicts somewhat with Zootopia's progressive individualist ethos, it would be unsurprising to see those clans amassing wealth and influence on society's margins rather than at the top.

That's the tidiest explanation for why there's a very tight-knit shrew clan with polar bear muscle and a lot of money, living in relative isolation in Little Rodentia.