You know what would have way more impact on housing affordability? Build it using traditional construction methods but make it 10 stories instead of 4 stories.
But the city will find some reason why that's absolutely unacceptable. Then they will go on to talk about how this is just fundamentally a difficult problem that they haven't found a solution for, but rest assured they are still looking for ways to solve it.
There is a practical aspect to building height. Berkeley is on an earthquake fault line, and buildings in the 6-15 storey range have a natural resonance that tends to match the frequency of earthquake waves.
I'm having difficulty finding references to this, so maybe it's not as big a deal as I thought?
The breakpoints have more to do with other parts of building codes. Wood framing is only strong enough to support three floors (unless you use cross laminated timber, which is a relatively new construction technology). Furthermore there are increasing requirements for fire suppression and accessibility as you add height. The breakpoints are basically either 2-floor duplex through quadplex that don't need elevators, or putting three floors of wood-framed apartments over a concrete or steel podium that contains commercial space and parking. Podium construction basically explains why so many 4 and 5 floor buildings get put up - it's significantly cheaper than the more expensive material required to make stuff strong enough for taller buildings.
Depends on the location. In the Bay Area a large portion of the cost is having your capital tied up for like 5+ years while trying to get your project approved.
That's not a real excuse. Tokyo is crisscrossed with fault-lines and they manage to build to quake code --the proof being all the healthy buildings despite frequent quakes.
But the city will find some reason why that's absolutely unacceptable. Then they will go on to talk about how this is just fundamentally a difficult problem that they haven't found a solution for, but rest assured they are still looking for ways to solve it.