This doesn't make sense to me, why is lowering rent by 30% any more "proof" that the building is not worth what's stated on the bill than having a 30% vacancy rate at the expected value? Aren't both subject to the same "market conditions" argument?
If the space is vacant, and the last known rent was $X, the assumption is that borrower is bad at advertising space, but a successor would be able to get it rented again at that rate.
OTOH, if the space is rented at 0.7 times $X, the tenants may have a long term lease that fixes that price for a significant time and even a savvy successor would have a hard time raising rents, so the valuation needs to be calculated based on current rent.
Wouldn't banks want to accurately assess these valuations so these types of "bad loans in actuality, good loans on paper" don't become a large portion of their balance sheet?
Maybe not all at once, but over time it seems like banks would want more accuracy on this.
And other parties further can be say pension funds, which on paper are forced to search for anything that make their goals look good enough. Thus not doing enough due diligence.
Everything is fine until it is not. And this has been seen time after time.