Seeing many scenarios of 4-plexes selling in the same price range as 5-plexes given the availability of 30-year, fixed rate debt (and likely better rates).
The 4 to 5 unit hurdle is what largely separates the owner occupant from the professional operator.
Sourcing commercial debt is much more complex than residential, creating higher barriers to entry and ultimately less (emotional) demand for these assets.
People are willing to pay up if they plan to live in the property.