Rather than speaking in generalities, I'll give a more specific example. There was a development of common-lot line dwellings that were cheaply built, have minimum amenities, and were packed in like sardines. They were hit hard when the 2008 downturn hit, and are predominantly occupied by tenants. Though that sounds like a failed development, there have been additional homes constructed here in the past few years, and they are also now rented. If they sell, it is priced based on their investment-potential, as owner-occupancy demand is poor, whereas investor demand is high. From that perspective, they aren't selling for a discount vs the "retail" price, but they are also not priced with upside to reflect potentially selling to an owner in the future. No one is attempting to sell off the individual units.
A property where there is a more balanced split between owners and tenants would, in theory, be more likely to be priced based on sellout and reflect a discount to the retail price. But, Illinois is in a strange place right now, as the outmigration from the past decade+ discouraged investment in that time, but losses seem to have stabilized or even reversed in some locations, so there is a shortage of rental units in many areas. As you know from the credit side, it is harder to get a mortgage now, due to the higher interest rates coupled with the higher home prices, so that has pushed many potential purchasers into rentals. The lower-priced units have experienced the largest increases, as an $800/ month unit would have been decent a couple of years ago, but now, that is often a Class C 1 BR unit. Many investors now come in from out of the area for even the small properties, so between the higher rents, lower vacancies, and higher investor demand that keeps multipliers high/ cap rates low, owner-occupants are not always keeping pace with the prices paid by investors.
IRT to GH's post (#66), I am admittedly referring more to common-lot line and even detached SF residential vs condos, so the condo fees aren't an issue. As the owner-occupants aren't "beating out" investors, the assessed values are (at least in theory) based on its investment potential, so the RE taxes aren't necessarily higher than what it would be for a similar apartment property on a unit basis.