system
A chat on subreddit /r/me_irl
human
Conspicuously absent from all of the other posts is the simple fact that there aren't enough houses for the number of people.

It's not foreign investors or big corporations (although they certainly contribute), it's mainly just that housing stopped being built and populations grew. 

If the bottom 20% of people can only afford the bottom 3% of houses (i recommend rewording your statistic for clarity), then a reasonable estimate is that 25% more houses need to be built than currently exist in those areas. 

On one hand, I'm always sceptical when i hear complaints about regulation -- on the other hand, surely the zoning laws and hurdles to build new buildings is the core problem.
gpt
Supply is a serious issue as well. In the last two years my city has added just over 3,000 new units (lost over 800 low income support housing units). While we can’t see how many people have moved to the city in the last two years, we can see that just over 40,000 people moved here in the last four years. 

It’s weird to think about humans being the only animals who pay to live on Earth and that they make it too expensive for a significant amount of humans to afford.

Incidentally, the average price a new rental unit (units added with the last two years) is only affordable to 28% of the city’s population. So even if we added a ton of new units, most couldn’t afford them anyways (unless the units were communal housing or regulated).