> The whole thing is silly, and the market is rife for a saner way to valuate properties.
That is not really how property valuation works.
A building is not worth whatever a mathematical formula outputs. Instead a building, or anything at all, is worth exactly how much other people are willing to pay for it. No more, no less.
Presumably, any prospective buyer who isn't stupid would be very much aware of the concept of a cyclical market, and they wouldn't change how much they valued a building just because the owner stupidly didn't rent it out during a downturn.
> Then, when a new actual rent is established and is being paid, you use that figure.
Nothing is stopping someone from simply doing that, and offering to buy the property for whatever this "better" formula outputs. And if this new formula is actually correct, then presumably such a person would be able to make tons of money from doing that.