Often, you/they get X (or you/they have X) are indeed interchangeable with there is X, or X exists. But in general, both alternatives (particularly, get) are informal, "slangy" usages.
As you'd expect by considering the literal meaning, in many contexts using you rather than they tends to suggest that you personally might be aware of/affected by whatever X is. Correspondingly, using they often implies X happens somewhere else, to other people; it doesn't directly affect us.
you get prostitution in any big city.
they get prostitutes in there.
there is prostitution in your country too.
In context, it wouldn't be ridiculous to replace all of those three usages with either of the other two.
Having said that, my advice would be to accept (but avoid using) either of the "personal pronoun" forms except in the context of a verbal exchange where a native speaker has already used one. It won't always "work" (sound natural). This is particularly so with they get, which is normally only used in contexts where it's possible to imagine some class of people ("they") who actually receive, experience, encounter X.
Thus, for example,...
It's not just an issue for developed nations. You get nuclear power in China too. (credible)
They get nuclear power in China as well, you know. (unlikely)
They have nuclear power in China too. (unexceptional, "literal", not "slangy")
Note that in those examples, #2 is "unlikely" because nuclear power isn't something anyone would normally "get" (#1 is "iffy", but acceptable to most because we're so familiar with the idiomatic usage). But if we replace nuclear power by, say, cholera, all three versions work (though #1 and #2 are still "slangy").