The simple answer is sometimes the correct one: for the most part, developers do not afford those particular condos. Or many of those who do they're single and childless. Vancouver's one of the most desirable places to live in the world, and so people preferentially migrate here (it's typical for people to be half-seriously astonished to meet a native), and so the market soars (plus there are some weird factors inflating it, arguably).

Although I've certainly known a few developers here to make over $100k. A few I've met professionally, and several of my old high-school friends. But this is not at all typical.