I read a book called "Nothing to Envy: Ordinary Lives in North Korea" by Barbara Demick, about North Koreans in the 1990s that escaped into China and told their story. One of the interesting parts of it is about the planned economy, and all the control the government exerts over the economy in NK.

There was a massive famine I didn't know about in the mid-to-late 1990s in NK, and millions died. During this period, an underground capitalism took over, where people were producing food in various ways, often grown in their own gardens, and then buying and selling from each other, with barter rates / prices determined by availability.

While I agree with you that countries can make rules that fix prices (or do whatever they want), there is an underlying set of mechanisms to supply and demand that are not derived from law, but logic. If I have 5 cupcakes, and there are 100 people that want them, unless someone points a gun at me and says "Sell them each for 5 cents" (while the 100 people all fight over who gets to pay), the natural incentive structure would essentially be an auction to figure out who is willing to pay the most, and then sell it to them. That's not some legal theory or set of laws, but rather the human condition.

Of course, it doesn't play out this way in reality. In reality, it all comes down to power, and those with power take whatever they want, but my point here is that supply and demand exist outside of a legal structure, and if there's only one electrician, and there's enough work for 10 electricians, that one electrician can server the richest 1/10 of those in need (and charge accordingly to select that 1/10), and it is rational to do so independent of any laws made. So much so, in fact, that laws are advisory, but the fundamental incentives are inherent.

This is why I like incentives more than rules: they're less brittle.