How expensive is Hong Kong?

I'm curious, how expensive is Hong Kong really? I've heard rumors that it's one of the most costly cities in the world to live in, but I'd like to get a better understanding. Are housing prices sky-high? How about the cost of food and transportation? And what about entertainment and leisure activities? Is it a place where even the basics can quickly add up, or are there ways to live comfortably without breaking the bank?