Value is certainly subjective. While it is possible you might find someone seeing a dollar as being worthless, just as they might give you a house for nothing in return, I don't expect you will find that to be scalable. If you have a thirst for all the dollars you can get your hands on, you are bound to go thirsty relying on this.

> Agreed, that limit is what total supply is.

There is a limit on supply, but also a limit on demand. That's why we call it "supply and demand", not just "supply". In a "normally functioning" market, demand actors start to drop out of the market as price rises.

In fact, you can see this happening in the housing market. A lot of people can't afford a house, so they are no longer participants in the housing market. They may still wish to own a house, but that's not demand, that's dreaming (or what you might call latent demand).

Hence why a shortage occurs when price is unable to rise. When price is unable to rise, there is no price-based mechanism to see that people leave the market, creating a situation where "demand exceeds supply". Which is why you will typically see alternate mechanisms step in instead, such as a lottery, or offering on the basis of first-come, first-served, to force people out some other way. A medical doctor with an ethical, and often legal, obligation to not allow price to rise is apt to use a needs-based mechanism, serving the patients in most need of care ahead of the richest patients with the common cold. That's certainly not the case in the housing market, though. Price is most definitely able to rise – demonstrably so.

> But notice it's possible to withhold something from being traded.

Of course – at which point it ceases to be supply. Just like, as above, it is possible to withhold on the other side of the transaction, at which point that ceases to be demand. This is exactly what the law of supply and demand describes.