As mentioned elsewhere in the thread, you are not short some dollar value but short some "survivalship house value" based upon your own subjective tolerance for what is a "minimally viable living situation."
If you live in the bay area, you may be short the "house value" equivalent of $500k, but living in Illinois you may be short the "house value" equivalent of $250k. Of course the location is part of the "minimally viable" part for certain people, but for others this is a less important part of "viability". Regardless, it's not a dollar value, it's "house living value", and anything beyond that part of the equity in the house you own (for most people: the majority of it) is speculation/investment into the real estate market.
If you live in the bay area, you may be short the "house value" equivalent of $500k, but living in Illinois you may be short the "house value" equivalent of $250k. Of course the location is part of the "minimally viable" part for certain people, but for others this is a less important part of "viability". Regardless, it's not a dollar value, it's "house living value", and anything beyond that part of the equity in the house you own (for most people: the majority of it) is speculation/investment into the real estate market.