Prices are set at the margin, where supply equals demand, in a free market. This also determines quantity.

I would say it is obvious more and more of something should be provided until the cost is too much for the next marginal use to bear – but the housing market in the US is a clear indication some people believe there to be some moral problem with this – that they, already living somewhere, deserve to see that area unchanged. Of course, they've also abandoned their moral responsibility to house the next generation, so they probably shouldn't be on such a high horse about their strange supply-side restrictions.

Of course, I could type all day about how, unless people expect a baby to take up a hammer and nail to venture out into the wilderness and claim a new home by their own efforts, they ought to be willing to expand housing supply in response to demand. It's also possible they want to live in a community with their family (and their friends, who might want to bring new people into this world as well), in which case they should expand supply in their own neighborhoods. But who am I to say people should keep in contact with family? I suppose that's a pretty personal suggestion, and clearly many people today want nothing to do with their children or grandchildren.

But my real purpose today isn't that – it's about non-marginal supply and demand. With market pricing, those in most desperate need receive the highest consumer surplus – unarguably the largest gift to the world's least well off in human history. No person gave this gift, it is a consequence of the structure of the system. But that system isn't obvious, and in fact didn't exist in any meaningful form for almost any of human history.

It also gives the largest producer surplus to those most efficient and austere. As much as people like to think capitalism requires lavish and ridiculous spending, truly, it strongly incentivizes the opposite. Prudence, and being willing to invest in the future, pay more dividends than almost anything. The only exception is the willingness to benefit others. That's the most prized virtue of modern international commerce – you get rewards in proportion to the rewards you provide others.

And this honestly works pretty well. Obviously you wouldn't run a family this way. You probably couldn't operate all your friendships like that, although certainly some could be handled this way informally. Of course, for friends, I imagine the proportion is greater than one – if someone gives me a thoughtful gift, I'd endeavor to outdo them, of course. But the proportionality is still there, in many cases. Close confidants are different – and there should be people we trust and stand by no matter what – but I'm not sufficiently expert on that topic to say a single thing.

The only reason I bring this up is to give a moral valence to price discrimination. I think the Quakers were (and are, of course) right to refuse it. There are many types of fairness, but paying according to demand meets fewer of those ideals.